chore: Release galdr version 0.3.0

Grid grammar:
- a base-36 glyph above a column's top operator tags it with a MIDI channel;
  '>' right of the tag makes the channel mono-legato (60 ms slide)
- operators below a '!' form the stereo master chain: Z delay, W chorus,
  plus any filter/shaper
- X: phase modulation by the cell to the left (and above), index from the right
- K: control envelope; left of an operator it drives that operator's left
  param (2KL5 = 303 filter sweep)
- per-note params: @ velocity, ^ key tracking, ? random; registers now read
  on the digit scale, so MIDI CC and UDP registers have full range

I/O:
- MIDI keeps the channel nibble
- UDP (orca's ';', port 49161): k7 register, *3 bang a column, @34O write
  a glyph, #name load a patch
- --stems n: one mono PipeWire node per channel tag (galdr.ch<tag>),
  sample-aligned with the master; separate nodes because a playback
  stream's AUX ports deliver no data in PipeWire 1.6
- the audio thread reconnects when PipeWire restarts; status line shows it
- patches: ~/hometaping/<date>.galdr by default, .galdr extension, Ctrl+S,
  GALDR_DEBUG=<file> logs events

Examples with render tests: drums, orchestra, acid.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Cargo.lock

@@ -320,7 +320,7 @@ dependencies = [
 
 [[package]]
 name = "galdr"
-version = "0.2.3"
+version = "0.3.0"
 dependencies = [
  "anyhow",
  "arc-swap",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "galdr"
-version = "0.2.3"
+version = "0.3.0"
 edition = "2021"
 description = "A terminal grid synthesizer: signal flows spatially through single-glyph unit generators, voiced by MIDI, rendered low-latency to PipeWire"
 license = "MIT"
@@ -11,7 +11,7 @@ codegen-units = 1
 
 [dependencies]
 anyhow = "1"
-pipewire = "0.10"
+pipewire = { version = "0.10", features = ["v0_3_49"] } # Buffer::requested
 midir = "0.10"
 arc-swap = "1.7"
 rtrb = "0.3"

README.md

@@ -1,14 +1,14 @@
 # galdr
 
 A terminal **grid synthesizer**. Signal flows downward through a field of
-single-glyph unit generators; every incoming MIDI note voices the whole grid;
-the mix is rendered low-latency to PipeWire. It is orca's voice — the same
-esoteric, spatial approach to programming, but for making sound instead of
-sending events.
+single-glyph unit generators; every incoming MIDI note voices the grid (or the
+columns tagged with its channel); the mix is rendered low-latency to PipeWire.
+It is orca's voice — the same esoteric, spatial approach to programming, but
+for making sound instead of sending events.
 
 ```
-orca-rs  ──MIDI/OSC/UDP──▶  galdr  ──PipeWire──▶  speakers
-   compose the pattern       voice it       (spectrust -p visualizes it)
+orca-rs  ──MIDI + UDP──▶  galdr  ──PipeWire──▶  speakers / stems
+   compose the pattern     voice it      (spectrust -p visualizes it)
 ```
 
 ## The grid
@@ -32,11 +32,179 @@ a constant parameter; a lowercase letter `a`–`z` reads MIDI CC (`a` = CC 0).
 | `D` | decimate / bitcrush | rate |
 | `G` | gain | amount |
 | `R` | ring modulator | ratio |
+| `X` | FM: sine at the note pitch, phase pushed by the cell to its **left** (and above) | — / index |
 | `M` | mix — adds the cell to its **left** | — |
+| `K` | control envelope: 1 at note-on, decays to a floor; no audio input | decay / floor |
 | `!` | output to master | — |
 
+`K` is the one operator whose output is a *param*: placed to the **left** of
+another operator it becomes that operator's left param, scaled 0–9. `2KL5` is
+a lowpass whose cutoff starts open and decays (2) to the floor, with
+resonance 5. That's the 303 filter envelope.
+
 Each `!` sums into the master, so parallel columns stack timbres or voices.
-A note plays every column at once.
+An untagged column plays on every MIDI channel.
+
+### Params
+
+A param cell is a digit `0`–`9` (constant), a lowercase letter `a`–`z` (a
+register: MIDI CC `a` = CC 0, or set over UDP), or one of three per-note
+values: `@` velocity, `^` key tracking (note number), `?` a random value rolled
+at note-on. All read on the same 0–9 scale, so `@L` is velocity-to-cutoff and
+`?O` detunes every hit a little differently.
+
+### Channel tags
+
+A base-36 glyph directly **above** a column's top operator is that column's
+MIDI channel: `0`–`9`, `a`–`f` for channels 1–16 (orca's numbering). The
+column then only voices notes on that channel. A `>` right of the tag makes
+the channel **mono-legato**: a note that overlaps the previous one slides the
+running voice to the new pitch over 60 ms without retriggering the envelopes,
+the 303 slide. From orca, make the step's note length longer than the gap.
+
+### Acid
+
+`examples/acid.galdr`, a 303 line on channel 1:
+
+```
+...0>
+...A.      saw (U for the square)
+.2KL@      K sweeps the cutoff (decay 2, floor open-to-closed); accent = velocity -> resonance
+...E1      short amp decay
+..3S.      overdrive
+...!.
+```
+
+```
+1....2....      column 0 is channel 1 (a filtered saw),
+A....O....      column 5 is channel 2 (a plain sine)
+L....E....
+E....!....
+!.........
+```
+
+### The master chain
+
+Operators placed **below** a column's `!` no longer run per voice: they
+process the summed stereo master, in series, in column order. Any filter or
+shaper works there, plus two master-only effects:
+
+| glyph | effect | left / right param |
+|---|---|---|
+| `Z` | delay | time (0 = 100 ms … 9 = 1 s) / feedback |
+| `W` | stereo chorus | rate / depth |
+
+```
+A
+!
+5L        lowpass on the whole mix
+3Z6       then a 400 ms delay with lots of feedback
+.W        then a slow chorus for width
+```
+
+Editing the grid recompiles and hot-swaps the running program without dropping
+audio. There is no embedded scope — run a spectrum analyzer (e.g. `spectrust`)
+on the side if you want one.
+
+## A drum kit (one drum per MIDI channel)
+
+A note voices every column tagged with its channel, so give each drum its own
+channel and let orca pick the channel per hit. `examples/drums.galdr`:
+
+```
+.0..9....a...b.
+.A..O9...N...N.
+@L5.EX9.6B5.8H.
+.E2..E1..E1..E0
+2S...!..3S...!.
+.!.......!.....
+```
+
+- **bass** (tag `0`, MIDI ch 1): saw → lowpass with the cutoff from velocity
+  (`@`) and resonance 5 → envelope, release 2 → soft clip 2 → out.
+- **kick** (tag `9`, ch 10): the left column is a sine into an envelope with
+  no `!`, it exists only as a modulator. The `X` next to it is a sine at the
+  note pitch, phase-modulated by that decaying signal with index 9: bright at
+  the hit, a clean low sine a moment later. Play it a low note (C1–C2).
+- **snare** (tag `a`, ch 11): noise → bandpass 6, resonance 5 → short
+  envelope → soft clip 3. A mid note sets the bandpass body.
+- **hats** (tag `b`, ch 12): noise → highpass 8 → envelope with release 0.
+  Note length from orca is the open/closed control.
+
+From orca, `:` with the channel glyph per drum, e.g. `:93C` for the kick,
+`:a3D` snare, `:b5F` hats, `:02C` bass. With `--stems 12` each drum also has
+its own `galdr.ch*` node to record.
+
+## An orchestra (the big example)
+
+`examples/orchestra.galdr` is ten sections on ten MIDI channels, each in a
+four-column block `[left param | chain | right param | gap]`, so every digit
+is a knob. It uses most of the vocabulary: velocity (`@`) into a filter and
+into an FM index, key tracking (`^`), per-note random (`?`), two modulator
+columns feeding `X`, registers set from orca (`k` and `z`), and a hall on the
+master chain (highpass, chorus, delay with feedback from `z`).
+
+```
+.0...1...2...3...44..5...6...7...8...9..
+.A...A...A2.2U...NO.1U..5U...O7..A...V..
+@L2.3L3.1EX@4L1.9HE36B6.6L1..EX3^L?.kL2.
+4E5.3E4..1E23E3.1E!.2E2.2E2..0E40E3.7E7.
+.!..2S...2S.1S..2G..1F...!....!..!..9G..
+1H...!....!..!...!...!...............!..
+2W3.....................................
+4Zz.....................................
+```
+
+| ch | tag | section | how |
+|---|---|---|---|
+| 1 | `0` | strings | saw, lowpass cutoff from velocity, slow envelope; the hall hangs under its `!` |
+| 2 | `1` | low strings | saw, lowpass 3/3, soft clip |
+| 3 | `2` | brass | a saw-envelope modulator column drives `X`, FM index from velocity |
+| 4 | `3` | horns | narrow pulse, lowpass, soft clip |
+| 5 | `4` | flute | breath noise (highpass, short env, gain) beside a sine |
+| 6 | `5` | reed | pulse width 1, resonant bandpass, fold |
+| 7 | `6` | clarinet | square, lowpass |
+| 8 | `7` | timpani | sine-envelope modulator into `X`, long release, play C1 to C2 |
+| 9 | `8` | harp | lowpass cutoff key-tracked, resonance random per pluck, pluck envelope |
+| 10 | `9` | choir | triangle, lowpass cutoff from register `k`, very slow envelope |
+
+Load it with `galdr examples/orchestra.galdr`, or over UDP with `#orchestra`
+once it sits in the patches directory. `;k5` and `;z3` from orca set the choir
+brightness and the hall feedback live.
+
+## Stems
+
+`--stems n` adds one mono PipeWire node per channel tag, `galdr.ch0` …
+`galdr.ch<n-1>` (named by the tag glyph), each carrying the dry sum of that
+channel's voices, sample-aligned with the master. They are not auto-connected:
+patch them in a graph tool, or record them with a multitrack recorder such as
+`stems`, and master the session later.
+
+## UDP control from orca
+
+galdr listens on UDP port 49161 (orca's `;` operator sends there). One
+datagram carries one or more commands, separated by whitespace or `;`:
+
+| command | effect |
+|---|---|
+| `k7` | set register `k` to 7 of 35 (base-36), read by `k` param cells |
+| `*3` | bang column 3: a 5 ms gate on that column alone, no note needed (drums, plucks) |
+| `@34O` | write glyph `O` at column 3, row 4 — orca patches the synth itself |
+| `@34.` | clear that cell |
+| `#verse` | load the patch `verse.galdr` from the patches directory |
+
+Bangs and register sets go straight into the audio thread; grid commands are
+applied by the editor and recompiled like a keystroke.
+
+## Patches
+
+A patch is plain text: one line per row, `.` for an empty cell, `#` lines
+ignored. `galdr file.galdr` opens one and `Ctrl+S` writes it back. With no
+file, galdr works on **today's** patch, `~/hometaping/<YYYY-MM-DD>.galdr`:
+opened at start if it exists, written by `Ctrl+S`. That is the same dated
+naming as the orca files kept in that directory, so a session's orca pattern
+and its galdr voice sort together. `#name` over UDP loads
+`<patches dir>/name.galdr` (`--patches` overrides the directory).
 
 Example — a filtered saw with an envelope:
 
@@ -47,22 +215,24 @@ E        ...enveloped by the note gate
 !        ...to master
 ```
 
-Editing the grid recompiles and hot-swaps the running program without dropping
-audio. There is no embedded scope — run a spectrum analyzer (e.g. `spectrust`)
-on the side if you want one.
-
 ## Usage
 
 ```
-galdr [--latency <frames>] [--poly <n>] [--rate <hz>] [--midi-name <s>]
+galdr [--latency <frames>] [--poly <n>] [--rate <hz>] [--stems <n>]
+      [--udp <port>] [--patches <dir>] [--midi-name <s>] [patch.galdr]
 ```
 
 galdr creates a virtual MIDI input port named **galdr**; connect orca or any
 sequencer/DAW to it. `--midi-name` connects to an existing port instead.
 
-Keys: cursor keys move; type a glyph to place it; Backspace clears; `?` toggles
-help; Esc quits. Resize the grid with `(` / `)` (width) and `_` / `+` (height)
+Keys: cursor keys move; type a glyph to place it; Backspace clears; `Ctrl+S`
+saves the patch; `?` toggles help; Esc quits. Resize the grid with `(` / `)` (width) and `_` / `+` (height)
 by one ruler division, or Ctrl+arrows by one cell (orca's bindings).
 
+galdr survives a PipeWire restart: the status line shows `PIPEWIRE DOWN —
+reconnecting…` and the stream comes back on its own, voices and master-chain
+state intact.
+
 Runtime deps: PipeWire and ALSA (MIDI). Built in Rust; reuses the native
-PipeWire path from spectrust.
+PipeWire path from spectrust. `GALDR_DEBUG=<file>` appends every event that
+reaches the engine, handy when orca and galdr disagree.

aur/PKGBUILD

@@ -1,6 +1,6 @@
 # Maintainer: Bendik Aagaard Lynghaug <bendik.lynghaug@gmail.com>
 pkgname=galdr
-pkgver=0.2.3
+pkgver=0.3.0
 pkgrel=1
 pkgdesc="Terminal grid synthesizer: signal flows through single-glyph unit generators, MIDI in, low-latency PipeWire out"
 arch=('x86_64' 'aarch64')

examples/acid.galdr

@@ -0,0 +1,9 @@
+# acid: a 303-style line on MIDI channel 1 (tag 0, '>' = slide on overlapping notes).
+# A saw > lowpass whose cutoff is swept by K (decay 2, floor 1); accent = velocity -> resonance (@);
+# short amp decay, overdrive. Swap A for U (square), raise K's decay for longer wows.
+...0>
+...A.
+.2KL@
+...E1
+..3S.
+...!.

examples/drums.galdr

@@ -0,0 +1,7 @@
+# bass (ch 1) | kick (ch 10) | snare (ch 11) | hats (ch 12): one drum per MIDI channel
+.0..9....a...b.
+.A..O9...N...N.
+@L5.EX9.6B5.8H.
+.E2..E1..E1..E0
+2S...!..3S...!.
+.!.......!.....

examples/orchestra.galdr

@@ -0,0 +1,21 @@
+# galdr orchestra: one section per MIDI channel (tag glyph above each column).
+# Sections are 4 columns: [left param | chain | right param | gap]. Tweak the digits;
+# @ = velocity, ^ = key tracking, ? = random per note, a-z = registers (MIDI CC / UDP).
+# strings  ch1  saw > lowpass(cutoff=@ velocity, res 2) > env 4/5 > out; the HALL below it: highpass 1 > chorus 2/3 > delay 4/fb from register z (orca: ;z3)
+# low str  ch2  saw > lowpass 3/3 > env 3/4 > soft clip 2
+# brass    ch3  left col = saw>env modulator (no !); right = X FM with index from @ velocity > env 1/2 > soft clip 2
+# horns    ch4  pulse width 2 > lowpass 4/1 > env 3/3 > soft clip 1
+# flute    ch5  left = noise breath (highpass 9 > env 1 > gain 2); right = sine > env rel 3
+# reed     ch6  narrow pulse 1 > bandpass 6/6 > env 2/2 > fold 1
+# clarinet ch7  square (width 5) > lowpass 6/1 > env 2/2
+# timpani  ch8  left = sine>env modulator; right = X index 3 > env 0/4 (play C1-C2)
+# harp     ch9  saw > lowpass: cutoff ^ key-tracked, resonance ? random per pluck > env 0/3
+# choir    ch10 triangle > lowpass: cutoff from register k (orca: ;k5), res 2 > slow env 7/7 > gain 9
+.0...1...2...3...44..5...6...7...8...9..
+.A...A...A2.2U...NO.1U..5U...O7..A...V..
+@L2.3L3.1EX@4L1.9HE36B6.6L1..EX3^L?.kL2.
+4E5.3E4..1E23E3.1E!.2E2.2E2..0E40E3.7E7.
+.!..2S...2S.1S..2G..1F...!....!..!..9G..
+1H...!....!..!...!...!...............!..
+2W3.....................................
+4Zz.....................................

src/audio.rs

@@ -1,11 +1,28 @@
-//! Low-latency PipeWire playback. The RT process callback drains input events,
-//! renders the voice mixer, and fills the output buffer. No allocation or locks
-//! on this path.
+//! Low-latency PipeWire playback. The RT process callbacks drain input events,
+//! render the voice mixer and master chain, and fill the output buffers. No
+//! allocation or locks on this path.
+//!
+//! Nodes: `galdr` is the stereo master (after the master chain) and is linked
+//! to the default sink by the session manager. With `--stems n`, one extra
+//! mono node per MIDI channel tag (`galdr.ch0` .. `galdr.ch<n-1>`, named by
+//! the base-36 glyph used in the grid) carries that channel's dry sum. Stem
+//! nodes are not auto-connected: patch or record them as you like.
+//!
+//! All streams of this client are driven on one data-loop thread, one
+//! callback each per graph cycle. The first callback of a cycle renders the
+//! frames for every output into a shared scratch buffer; the others copy
+//! their channel out of it, so master and stems stay sample-aligned.
+//!
+//! If the daemon goes away (restart, crash) the connection is torn down and
+//! rebuilt every second until it is back; the engine state survives.
 
-use std::sync::atomic::{AtomicU32, Ordering};
+use std::cell::RefCell;
+use std::rc::Rc;
+use std::sync::atomic::{AtomicBool, AtomicU32, Ordering};
 use std::sync::mpsc::Sender;
 use std::sync::Arc;
 use std::thread;
+use std::time::Duration;
 
 use arc_swap::ArcSwap;
 use pipewire as pw;
@@ -15,50 +32,180 @@ use rtrb::Consumer;
 use spa::param::audio::{AudioFormat, AudioInfoRaw};
 
 use crate::dsp::Program;
-use crate::engine::{Engine, Event};
+use crate::engine::{Engine, Event, CHANNELS};
 
 pub type Shared = Arc<ArcSwap<Program>>;
 
-#[allow(clippy::too_many_arguments)]
+/// Largest cycle PipeWire will ask for (clock.quantum-limit default).
+const MAX_FRAMES: usize = 8192;
+
+pub struct Config {
+    pub sr: u32,
+    pub latency: u32,
+    pub poly: usize,
+    /// Number of per-channel stem nodes (0..=16).
+    pub stems: usize,
+}
+
+/// Start the audio thread. Returns once the first PipeWire connection is up
+/// (or with the error if it never comes up). Afterwards the thread keeps the
+/// engine and reconnects on its own; `connected` tells the UI which state it
+/// is in.
 pub fn spawn(
     prog: Shared,
     events: Consumer<Event>,
     voices: Arc<AtomicU32>,
-    sr: u32,
-    channels: u8,
-    latency: u32,
-    poly: usize,
+    connected: Arc<AtomicBool>,
+    cfg: Config,
 ) -> Result<(), String> {
     let (ready_tx, ready_rx) = std::sync::mpsc::channel::<Result<(), String>>();
     thread::Builder::new()
         .name("galdr-audio".into())
         .spawn(move || {
-            if let Err(e) =
-                run(prog, events, voices, sr, channels, latency, poly, ready_tx.clone())
-            {
-                let _ = ready_tx.send(Err(e));
+            let render = Rc::new(RefCell::new(Render {
+                engine: Engine::new(cfg.poly, cfg.sr as f32),
+                events,
+                prog,
+                voices,
+                latency: cfg.latency as usize,
+                cycle: 0,
+                frames: 0,
+                master: vec![[0.0; 2]; MAX_FRAMES],
+                stems: vec![[0.0; CHANNELS]; MAX_FRAMES],
+            }));
+            let mut first = Some(ready_tx);
+            loop {
+                let outcome = run(&render, &cfg, &connected, &mut first);
+                connected.store(false, Ordering::Relaxed);
+                match outcome {
+                    Err(e) => {
+                        if let Some(tx) = first.take() {
+                            // never connected: report once and give up
+                            let _ = tx.send(Err(e));
+                            return;
+                        }
+                        eprintln!("\r\n[galdr] PipeWire connection lost ({e}); reconnecting\r");
+                    }
+                    Ok(()) => eprintln!("\r\n[galdr] PipeWire connection closed; reconnecting\r"),
+                }
+                thread::sleep(Duration::from_secs(1));
             }
         })
         .map_err(|e| format!("spawn audio thread: {e}"))?;
-    ready_rx.recv().map_err(|_| "audio thread exited before start".to_string())?
+    ready_rx
+        .recv()
+        .map_err(|_| "audio thread exited before start".to_string())?
 }
 
-#[allow(clippy::too_many_arguments)]
-fn run(
+/// One graph cycle's worth of rendered audio, shared by all stream callbacks.
+struct Render {
+    engine: Engine,
+    events: Consumer<Event>,
     prog: Shared,
-    mut events: Consumer<Event>,
     voices: Arc<AtomicU32>,
-    sr: u32,
-    channels: u8,
-    latency: u32,
-    poly: usize,
-    ready: Sender<Result<(), String>>,
+    latency: usize,
+    /// Cycle counter: bumped each time a new cycle is rendered.
+    cycle: u64,
+    frames: usize,
+    master: Vec<[f32; 2]>,
+    stems: Vec<[f32; CHANNELS]>,
+}
+
+impl Render {
+    /// Render `want` frames if this callback is the first of a new cycle.
+    /// `seen` is the calling stream's last rendered cycle.
+    fn ensure(&mut self, seen: u64, want: usize) {
+        if seen != self.cycle {
+            return; // another stream already rendered this cycle
+        }
+        // Render only what the graph asked for this cycle. The mapped
+        // buffer is sized by clock.quantum-limit (8192 frames by default),
+        // so filling it whole would do ~32x the work of a 256-frame
+        // quantum and PipeWire would drop everything past the quantum:
+        // choppy output and envelopes that race through their stages.
+        let want = if want > 0 { want } else { self.latency }.min(MAX_FRAMES);
+        let program = self.prog.load();
+        // Drain all pending input events once per cycle.
+        while let Ok(ev) = self.events.pop() {
+            self.engine.apply(ev);
+        }
+        for f in 0..want {
+            self.master[f] = self.engine.render(&program);
+            self.stems[f] = self.engine.stems;
+        }
+        self.frames = want;
+        self.cycle += 1;
+        self.voices
+            .store(self.engine.active_voices() as u32, Ordering::Relaxed);
+    }
+}
+
+fn format_pod(sr: u32, positions: &[u32]) -> Result<Vec<u8>, String> {
+    let mut audio_info = AudioInfoRaw::new();
+    audio_info.set_format(AudioFormat::F32LE);
+    audio_info.set_rate(sr);
+    audio_info.set_channels(positions.len() as u32);
+    let mut pos = [0u32; spa::sys::SPA_AUDIO_MAX_CHANNELS as usize];
+    pos[..positions.len()].copy_from_slice(positions);
+    audio_info.set_position(pos);
+    let obj = spa::pod::Object {
+        type_: spa::utils::SpaTypes::ObjectParamFormat.as_raw(),
+        id: spa::param::ParamType::EnumFormat.as_raw(),
+        properties: audio_info.into(),
+    };
+    Ok(spa::pod::serialize::PodSerializer::serialize(
+        std::io::Cursor::new(Vec::new()),
+        &spa::pod::Value::Object(obj),
+    )
+    .map_err(|e| format!("pod: {e}"))?
+    .0
+    .into_inner())
+}
+
+/// The base-36 glyph for a channel index, as used for grid tags.
+pub fn glyph(ch: usize) -> char {
+    b"0123456789abcdefghijklmnopqrstuvwxyz"[ch % 36] as char
+}
+
+/// One connection to the daemon: build the streams, run the loop until the
+/// connection fails (core error, stream error), then return so the caller
+/// can retry with the same `Render`.
+fn run(
+    render: &Rc<RefCell<Render>>,
+    cfg: &Config,
+    connected: &Arc<AtomicBool>,
+    ready: &mut Option<Sender<Result<(), String>>>,
 ) -> Result<(), String> {
     pw::init();
     let mainloop = pw::main_loop::MainLoopRc::new(None).map_err(|e| format!("mainloop: {e}"))?;
-    let context = pw::context::ContextRc::new(&mainloop, None).map_err(|e| format!("context: {e}"))?;
-    let core = context.connect_rc(None).map_err(|e| format!("connect PipeWire: {e}"))?;
+    let context =
+        pw::context::ContextRc::new(&mainloop, None).map_err(|e| format!("context: {e}"))?;
+    let core = context
+        .connect_rc(None)
+        .map_err(|e| format!("connect PipeWire: {e}"))?;
 
+    let sr = cfg.sr;
+    let latency = cfg.latency;
+    let stems = cfg.stems.min(CHANNELS);
+
+    // The daemon going away surfaces as an error on the core object itself
+    // (id 0). Quit the loop; the caller reconnects.
+    let ml = mainloop.clone();
+    let _core_listener = core
+        .add_listener_local()
+        .error(move |id, _seq, res, msg| {
+            if id == 0 {
+                eprintln!("\r\n[galdr] PipeWire core error {res}: {msg}\r");
+                ml.quit();
+            }
+        })
+        .register();
+
+    // Keep every stream and listener alive for the connection's lifetime.
+    let mut streams = Vec::new();
+    let mut listeners = Vec::new();
+
+    // ---- master: stereo, auto-connected ----
     let props = properties! {
         *pw::keys::MEDIA_TYPE => "Audio",
         *pw::keys::MEDIA_CATEGORY => "Playback",
@@ -66,64 +213,56 @@ fn run(
         *pw::keys::NODE_NAME => "galdr",
         *pw::keys::NODE_LATENCY => format!("{latency}/{sr}"),
     };
-    let stream = pw::stream::StreamBox::new(&core, "galdr", props).map_err(|e| format!("stream: {e}"))?;
-
-    let ch = channels.max(1) as usize;
-    let mut engine = Engine::new(poly, sr as f32);
-
-    let _listener = stream
+    let stream =
+        pw::stream::StreamBox::new(&core, "galdr", props).map_err(|e| format!("stream: {e}"))?;
+    let r = render.clone();
+    let mut seen: u64 = render.borrow().cycle;
+    let ml = mainloop.clone();
+    let listener = stream
         .add_local_listener_with_user_data(())
-        .process(move |stream, _| {
-            let Some(mut buffer) = stream.dequeue_buffer() else { return };
-            let datas = buffer.datas_mut();
-            let Some(data) = datas.first_mut() else { return };
-            let stride = ch * 4;
-            let program = prog.load();
-
-            // Drain all pending input events once per buffer.
-            while let Ok(ev) = events.pop() {
-                engine.apply(ev);
+        .state_changed(move |_, _, _old, new| {
+            if let pw::stream::StreamState::Error(e) = new {
+                eprintln!("\r\n[galdr] stream error: {e}\r");
+                ml.quit();
             }
-
-            let mut n_frames = 0usize;
+        })
+        .process(move |stream, _| {
+            let Some(mut buffer) = stream.dequeue_buffer() else {
+                return;
+            };
+            let requested = buffer.requested() as usize;
+            let datas = buffer.datas_mut();
+            let Some(data) = datas.first_mut() else {
+                return;
+            };
+            let stride = 2 * 4;
+            let mut r = r.borrow_mut();
+            r.ensure(seen, requested);
+            seen = r.cycle;
+            let mut n = 0usize;
             if let Some(slice) = data.data() {
-                n_frames = slice.len() / stride;
-                for f in 0..n_frames {
-                    let smp = engine.render(&program);
-                    let bytes = smp.to_le_bytes();
-                    for c in 0..ch {
-                        let o = f * stride + c * 4;
-                        slice[o..o + 4].copy_from_slice(&bytes);
-                    }
+                n = r.frames.min(slice.len() / stride);
+                for (f, m) in r.master[..n].iter().enumerate() {
+                    let o = f * stride;
+                    slice[o..o + 4].copy_from_slice(&m[0].to_le_bytes());
+                    slice[o + 4..o + 8].copy_from_slice(&m[1].to_le_bytes());
                 }
             }
             let chunk = data.chunk_mut();
             *chunk.offset_mut() = 0;
             *chunk.stride_mut() = stride as _;
-            *chunk.size_mut() = (stride * n_frames) as _;
-            voices.store(engine.active_voices() as u32, Ordering::Relaxed);
+            *chunk.size_mut() = (stride * n) as _;
         })
         .register()
         .map_err(|e| format!("listener: {e}"))?;
-
-    let mut audio_info = AudioInfoRaw::new();
-    audio_info.set_format(AudioFormat::F32LE);
-    audio_info.set_rate(sr);
-    audio_info.set_channels(channels as u32);
-    let obj = spa::pod::Object {
-        type_: spa::utils::SpaTypes::ObjectParamFormat.as_raw(),
-        id: spa::param::ParamType::EnumFormat.as_raw(),
-        properties: audio_info.into(),
-    };
-    let values: Vec<u8> = spa::pod::serialize::PodSerializer::serialize(
-        std::io::Cursor::new(Vec::new()),
-        &spa::pod::Value::Object(obj),
-    )
-    .map_err(|e| format!("pod: {e}"))?
-    .0
-    .into_inner();
+    let values = format_pod(
+        sr,
+        &[
+            spa::sys::SPA_AUDIO_CHANNEL_FL,
+            spa::sys::SPA_AUDIO_CHANNEL_FR,
+        ],
+    )?;
     let mut params = [Pod::from_bytes(&values).ok_or("bad pod")?];
-
     stream
         .connect(
             spa::utils::Direction::Output,
@@ -134,8 +273,78 @@ fn run(
             &mut params,
         )
         .map_err(|e| format!("connect stream: {e}"))?;
+    listeners.push(listener);
+    streams.push(stream);
 
-    let _ = ready.send(Ok(()));
+    // ---- stems: mono, one node per channel tag, not auto-connected ----
+    for s in 0..stems {
+        let name = format!("galdr.ch{}", glyph(s));
+        let props = properties! {
+            *pw::keys::MEDIA_TYPE => "Audio",
+            *pw::keys::MEDIA_CATEGORY => "Playback",
+            *pw::keys::MEDIA_ROLE => "Music",
+            *pw::keys::NODE_NAME => name.as_str(),
+            *pw::keys::NODE_DESCRIPTION => format!("galdr stem: MIDI channel tag {}", glyph(s)),
+            *pw::keys::NODE_AUTOCONNECT => "false",
+            *pw::keys::NODE_LATENCY => format!("{latency}/{sr}"),
+        };
+        let stream = pw::stream::StreamBox::new(&core, &name, props)
+            .map_err(|e| format!("stem stream: {e}"))?;
+        let r = render.clone();
+        let mut seen: u64 = render.borrow().cycle;
+        let ml = mainloop.clone();
+        let listener = stream
+            .add_local_listener_with_user_data(())
+            .state_changed(move |_, _, _old, new| {
+                if let pw::stream::StreamState::Error(e) = new {
+                    eprintln!("\r\n[galdr] stem stream error: {e}\r");
+                    ml.quit();
+                }
+            })
+            .process(move |stream, _| {
+                let Some(mut buffer) = stream.dequeue_buffer() else {
+                    return;
+                };
+                let requested = buffer.requested() as usize;
+                let datas = buffer.datas_mut();
+                let Some(data) = datas.first_mut() else {
+                    return;
+                };
+                let mut r = r.borrow_mut();
+                r.ensure(seen, requested);
+                seen = r.cycle;
+                let mut n = 0usize;
+                if let Some(slice) = data.data() {
+                    n = r.frames.min(slice.len() / 4);
+                    for (f, st) in r.stems[..n].iter().enumerate() {
+                        slice[f * 4..f * 4 + 4].copy_from_slice(&st[s].to_le_bytes());
+                    }
+                }
+                let chunk = data.chunk_mut();
+                *chunk.offset_mut() = 0;
+                *chunk.stride_mut() = 4;
+                *chunk.size_mut() = (4 * n) as _;
+            })
+            .register()
+            .map_err(|e| format!("stem listener: {e}"))?;
+        let values = format_pod(sr, &[spa::sys::SPA_AUDIO_CHANNEL_MONO])?;
+        let mut params = [Pod::from_bytes(&values).ok_or("bad pod")?];
+        stream
+            .connect(
+                spa::utils::Direction::Output,
+                None,
+                pw::stream::StreamFlags::MAP_BUFFERS | pw::stream::StreamFlags::RT_PROCESS,
+                &mut params,
+            )
+            .map_err(|e| format!("connect stem stream: {e}"))?;
+        listeners.push(listener);
+        streams.push(stream);
+    }
+
+    connected.store(true, Ordering::Relaxed);
+    if let Some(tx) = ready.take() {
+        let _ = tx.send(Ok(()));
+    }
     mainloop.run();
     Ok(())
 }

src/engine.rs

@@ -1,12 +1,36 @@
-//! Voice allocation and the polyphonic mixer. Owned by the audio thread.
+//! Voice allocation, the polyphonic mixer, per-channel stems and the master
+//! chain. Owned by the audio thread.
 
-use crate::dsp::{eval_voice, Program, Voice};
+use crate::dsp::{eval_post, eval_voice, Program, Voice, BUF_SECONDS, MAX_BUFS, MAX_STATE};
 
-#[derive(Clone, Copy)]
+pub const CHANNELS: usize = 16;
+
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub enum Event {
-    NoteOn { note: u8, vel: u8 },
-    NoteOff { note: u8 },
-    Cc { idx: u8, val: u8 },
+    NoteOn {
+        ch: u8,
+        note: u8,
+        vel: u8,
+    },
+    NoteOff {
+        ch: u8,
+        note: u8,
+    },
+    /// MIDI control change -> register (0..=127)
+    Cc {
+        idx: u8,
+        val: u8,
+    },
+    /// Register set from UDP (0.0..=1.0)
+    Reg {
+        idx: u8,
+        val: f32,
+    },
+    /// Retrigger one column, no note: a short gate at the column channel's
+    /// last pitch.
+    Bang {
+        col: u8,
+    },
 }
 
 pub struct Engine {
@@ -14,15 +38,35 @@ pub struct Engine {
     regs: Vec<f32>,
     sr: f32,
     clock: u64,
+    last_freq: [f32; CHANNELS],
+    /// Dry per-MIDI-channel sums of the last rendered frame.
+    pub stems: [f32; CHANNELS],
+    post_state: Vec<f32>,
+    bufs: Vec<Vec<f32>>,
+    buf_len: usize,
+    buf_pos: usize,
+    /// Copied from the program each render: which channels slide.
+    legato: [bool; CHANNELS],
+    /// Per-sample glide coefficient (~60 ms).
+    glide: f32,
 }
 
 impl Engine {
     pub fn new(poly: usize, sr: f32) -> Self {
+        let buf_len = (sr * BUF_SECONDS) as usize;
         Engine {
             voices: (0..poly).map(|_| Voice::new()).collect(),
             regs: vec![0.0; 128],
             sr,
             clock: 0,
+            last_freq: [220.0; CHANNELS],
+            stems: [0.0; CHANNELS],
+            post_state: vec![0.0; MAX_STATE],
+            bufs: (0..MAX_BUFS).map(|_| vec![0.0; 2 * buf_len]).collect(),
+            buf_len,
+            buf_pos: 0,
+            legato: [false; CHANNELS],
+            glide: 1.0 / (0.06 * sr),
         }
     }
 
@@ -30,65 +74,158 @@ impl Engine {
         self.voices.iter().filter(|v| v.active).count()
     }
 
+    /// A free voice, else the oldest one (stolen).
+    fn allocate(&mut self) -> usize {
+        self.clock += 1;
+        self.voices
+            .iter()
+            .position(|v| !v.active)
+            .unwrap_or_else(|| {
+                let mut best = 0;
+                for i in 1..self.voices.len() {
+                    if self.voices[i].age < self.voices[best].age {
+                        best = i;
+                    }
+                }
+                best
+            })
+    }
+
+    fn start(&mut self, idx: usize, ch: u8, note: u8, freq: f32, vel: f32) {
+        let clock = self.clock;
+        let v = &mut self.voices[idx];
+        v.active = true;
+        v.ch = ch;
+        v.note = note;
+        v.freq = freq;
+        v.gate = 1.0;
+        v.vel = vel;
+        v.age = clock;
+        v.only_col = None;
+        v.trig_left = 0;
+        v.resolve_ch = false;
+        v.t = 0;
+        v.target = freq;
+        v.rand = v.next_rand();
+        // fresh phases/env so a stolen voice doesn't click from old state
+        for x in v.state.iter_mut() {
+            *x = 0.0;
+        }
+        v.env_level = 0.0;
+    }
+
     pub fn apply(&mut self, ev: Event) {
         match ev {
-            Event::NoteOn { note, vel } => {
-                self.clock += 1;
-                // Prefer a free voice, else steal the oldest.
-                let idx = self
-                    .voices
-                    .iter()
-                    .position(|v| !v.active)
-                    .unwrap_or_else(|| {
-                        let mut best = 0;
-                        for i in 1..self.voices.len() {
-                            if self.voices[i].age < self.voices[best].age {
-                                best = i;
-                            }
-                        }
-                        best
-                    });
-                let v = &mut self.voices[idx];
-                v.active = true;
-                v.note = note;
-                v.freq = 440.0 * 2f32.powf((note as f32 - 69.0) / 12.0);
-                v.gate = 1.0;
-                v.vel = vel as f32 / 127.0;
-                v.age = self.clock;
-                // fresh phases/env so a stolen voice doesn't click from old state
-                for x in v.state.iter_mut() {
-                    *x = 0.0;
+            Event::NoteOn { ch, note, vel } => {
+                let ch = ch % CHANNELS as u8;
+                let freq = 440.0 * 2f32.powf((note as f32 - 69.0) / 12.0);
+                self.last_freq[ch as usize] = freq;
+                // Slide: on a legato channel an overlapping note retunes the
+                // held voice instead of starting one (envelopes keep running).
+                if self.legato[ch as usize] {
+                    if let Some(v) = self
+                        .voices
+                        .iter_mut()
+                        .find(|v| v.active && v.ch == ch && v.gate > 0.5 && v.only_col.is_none())
+                    {
+                        v.target = freq;
+                        v.note = note;
+                        return;
+                    }
                 }
-                v.env_level = 0.0;
+                let idx = self.allocate();
+                self.start(idx, ch, note, freq, vel as f32 / 127.0);
             }
-            Event::NoteOff { note } => {
+            Event::NoteOff { ch, note } => {
+                let ch = ch % CHANNELS as u8;
                 for v in self.voices.iter_mut() {
-                    if v.active && v.note == note {
+                    if v.active && v.note == note && v.ch == ch && v.only_col.is_none() {
                         v.gate = 0.0;
                     }
                 }
             }
             Event::Cc { idx, val } => {
-                self.regs[idx as usize] = val as f32 / 127.0;
+                self.regs[idx as usize & 127] = val as f32 / 127.0;
+            }
+            Event::Reg { idx, val } => {
+                self.regs[idx as usize & 127] = val.clamp(0.0, 1.0);
+            }
+            Event::Bang { col } => {
+                // A bang voice plays one column at the most recent pitch
+                // heard, with a 5 ms gate. Its channel (hence its stem) is
+                // resolved from the column's tag at the next render.
+                let freq = self.last_freq.iter().cloned().fold(0.0, f32::max).max(55.0);
+                let idx = self.allocate();
+                let note = (69.0 + 12.0 * (freq / 440.0).log2())
+                    .round()
+                    .clamp(0.0, 127.0) as u8;
+                self.start(idx, 0, note, freq, 1.0);
+                let v = &mut self.voices[idx];
+                v.only_col = Some(col);
+                v.trig_left = (self.sr * 0.005) as u32;
+                v.resolve_ch = true;
             }
         }
     }
 
+    /// Render one stereo frame of the master (after the master chain) and
+    /// refresh `stems` with the dry per-channel sums.
     #[inline]
-    pub fn render(&mut self, prog: &Program) -> f32 {
+    pub fn render(&mut self, prog: &Program) -> [f32; 2] {
         let mut mix = 0.0f32;
+        self.stems = [0.0; CHANNELS];
+        self.legato = prog.legato;
         for v in self.voices.iter_mut() {
             if !v.active {
                 continue;
             }
-            mix += eval_voice(v, prog, &self.regs, self.sr);
+            if v.target != v.freq {
+                v.freq += (v.target - v.freq) * self.glide;
+                if (v.target - v.freq).abs() < 0.01 {
+                    v.freq = v.target;
+                }
+            }
+            if v.resolve_ch {
+                v.resolve_ch = false;
+                if let Some(col) = v.only_col {
+                    v.ch = prog
+                        .nodes
+                        .iter()
+                        .find(|n| n.col == col)
+                        .and_then(|n| n.ch)
+                        .unwrap_or(0);
+                }
+            }
+            let y = eval_voice(v, prog, &self.regs, self.sr);
+            mix += y;
+            self.stems[v.ch as usize] += y;
+            if v.trig_left > 0 {
+                v.trig_left -= 1;
+                if v.trig_left == 0 {
+                    v.gate = 0.0;
+                }
+            }
             // Reap voices whose gate is closed and envelope has decayed.
             if v.gate < 0.5 && v.env_level < 1e-4 {
                 v.active = false;
             }
         }
+        for s in self.stems.iter_mut() {
+            *s = (*s * 0.3).tanh();
+        }
+        let m = mix * 0.3;
+        let y = eval_post(
+            prog,
+            [m, m],
+            &self.regs,
+            &mut self.post_state,
+            &mut self.bufs,
+            self.buf_len,
+            &mut self.buf_pos,
+            self.sr,
+        );
         // Gentle headroom limiter.
-        (mix * 0.3).tanh()
+        [y[0].tanh(), y[1].tanh()]
     }
 }
 
@@ -121,7 +258,11 @@ mod tests {
     #[test]
     fn noteon_maps_a4_to_440() {
         let mut e = Engine::new(4, 48000.0);
-        e.apply(Event::NoteOn { note: 69, vel: 100 });
+        e.apply(Event::NoteOn {
+            ch: 0,
+            note: 69,
+            vel: 100,
+        });
         assert!((e.first_freq().unwrap() - 440.0).abs() < 0.01);
         assert_eq!(e.active_voices(), 1);
     }
@@ -130,10 +271,31 @@ mod tests {
     fn noteoff_reaps_gated_voice() {
         let p = compile(&grid_from("A\n!")); // no envelope -> gate reaps immediately
         let mut e = Engine::new(4, 48000.0);
-        e.apply(Event::NoteOn { note: 60, vel: 100 });
+        e.apply(Event::NoteOn {
+            ch: 0,
+            note: 60,
+            vel: 100,
+        });
         e.render(&p);
         assert_eq!(e.active_voices(), 1);
-        e.apply(Event::NoteOff { note: 60 });
+        e.apply(Event::NoteOff { ch: 0, note: 60 });
+        e.render(&p);
+        assert_eq!(e.active_voices(), 0);
+    }
+
+    #[test]
+    fn noteoff_matches_channel() {
+        let p = compile(&grid_from("A\n!"));
+        let mut e = Engine::new(4, 48000.0);
+        e.apply(Event::NoteOn {
+            ch: 1,
+            note: 60,
+            vel: 100,
+        });
+        e.apply(Event::NoteOff { ch: 2, note: 60 }); // wrong channel: ignored
+        e.render(&p);
+        assert_eq!(e.active_voices(), 1);
+        e.apply(Event::NoteOff { ch: 1, note: 60 });
         e.render(&p);
         assert_eq!(e.active_voices(), 0);
     }
@@ -141,17 +303,27 @@ mod tests {
     #[test]
     fn monophonic_steals_the_oldest_voice() {
         let mut e = Engine::new(1, 48000.0);
-        e.apply(Event::NoteOn { note: 60, vel: 100 });
-        e.apply(Event::NoteOn { note: 72, vel: 100 });
+        e.apply(Event::NoteOn {
+            ch: 0,
+            note: 60,
+            vel: 100,
+        });
+        e.apply(Event::NoteOn {
+            ch: 0,
+            note: 72,
+            vel: 100,
+        });
         assert_eq!(e.active_voices(), 1);
         assert!((e.first_freq().unwrap() - 440.0 * 2f32.powf((72.0 - 69.0) / 12.0)).abs() < 0.01);
     }
 
     #[test]
-    fn cc_writes_register() {
+    fn cc_and_udp_write_registers() {
         let mut e = Engine::new(2, 48000.0);
         e.apply(Event::Cc { idx: 0, val: 127 });
         assert!((e.reg(0) - 1.0).abs() < 1e-6);
+        e.apply(Event::Reg { idx: 1, val: 0.5 });
+        assert!((e.reg(1) - 0.5).abs() < 1e-6);
     }
 
     #[test]
@@ -159,7 +331,143 @@ mod tests {
         // many stacked saws would exceed 1.0 without the limiter
         let p = compile(&grid_from("A.A.A.A\n!.!.!.!"));
         let mut e = Engine::new(4, 48000.0);
-        e.apply(Event::NoteOn { note: 60, vel: 127 });
-        assert!(e.render(&p).abs() <= 1.0);
+        e.apply(Event::NoteOn {
+            ch: 0,
+            note: 60,
+            vel: 127,
+        });
+        let y = e.render(&p);
+        assert!(y[0].abs() <= 1.0 && y[1].abs() <= 1.0);
+    }
+
+    #[test]
+    fn stems_follow_the_note_channel() {
+        let p = compile(&grid_from("A\n!"));
+        let mut e = Engine::new(4, 48000.0);
+        e.apply(Event::NoteOn {
+            ch: 3,
+            note: 60,
+            vel: 127,
+        });
+        e.render(&p);
+        assert!(e.stems[3].abs() > 0.1);
+        assert!(e.stems.iter().enumerate().all(|(i, s)| i == 3 || *s == 0.0));
+    }
+
+    #[test]
+    fn tagged_columns_split_by_channel() {
+        // col 0 -> channel 1 ('1'), col 2 -> channel 2 ('2')
+        let p = compile(&grid_from("1.2\nA.A\n!.!"));
+        let mut e = Engine::new(4, 48000.0);
+        e.apply(Event::NoteOn {
+            ch: 1,
+            note: 60,
+            vel: 127,
+        });
+        let y = e.render(&p);
+        assert!(y[0].abs() > 0.1);
+        assert!(e.stems[1].abs() > 0.1 && e.stems[2] == 0.0);
+        let mut e = Engine::new(4, 48000.0);
+        e.apply(Event::NoteOn {
+            ch: 5,
+            note: 60,
+            vel: 127,
+        });
+        assert_eq!(e.render(&p), [0.0, 0.0]);
+    }
+
+    #[test]
+    fn bang_plays_one_column_briefly() {
+        let p = compile(&grid_from("A.A\n!.!"));
+        let mut e = Engine::new(4, 48000.0);
+        e.apply(Event::Bang { col: 2 });
+        let y = e.render(&p);
+        assert!(y[0].abs() > 0.1);
+        for _ in 0..300 {
+            e.render(&p);
+        }
+        assert_eq!(e.active_voices(), 0, "bang voice gates off after 5 ms");
+    }
+
+    #[test]
+    fn bang_lands_in_the_tagged_stem() {
+        let p = compile(&grid_from("3\nA\n!"));
+        let mut e = Engine::new(4, 48000.0);
+        e.apply(Event::Bang { col: 0 });
+        e.render(&p);
+        assert!(e.stems[3].abs() > 0.1);
+        assert_eq!(e.stems[0], 0.0);
+    }
+
+    #[test]
+    fn legato_channel_slides_instead_of_retriggering() {
+        let p = compile(&grid_from("1>\nA.\n!."));
+        let mut e = Engine::new(4, 48000.0);
+        e.apply(Event::NoteOn {
+            ch: 1,
+            note: 60,
+            vel: 100,
+        });
+        e.render(&p);
+        e.apply(Event::NoteOn {
+            ch: 1,
+            note: 72,
+            vel: 100,
+        }); // overlapping: slide
+        assert_eq!(e.active_voices(), 1);
+        let f0 = e.first_freq().unwrap();
+        for _ in 0..24000 {
+            e.render(&p);
+        }
+        let f1 = e.first_freq().unwrap();
+        assert!(
+            f0 < 300.0 && (f1 - 523.25).abs() < 0.5,
+            "glided {f0} -> {f1}"
+        );
+        // the old note's off is ignored, the new note's off releases
+        e.apply(Event::NoteOff { ch: 1, note: 60 });
+        e.render(&p);
+        assert_eq!(e.active_voices(), 1);
+        e.apply(Event::NoteOff { ch: 1, note: 72 });
+        e.render(&p);
+        assert_eq!(e.active_voices(), 0);
+        // without the flag the same channel is polyphonic
+        let p2 = compile(&grid_from("1\nA\n!"));
+        let mut e = Engine::new(4, 48000.0);
+        e.apply(Event::NoteOn {
+            ch: 1,
+            note: 60,
+            vel: 100,
+        });
+        e.render(&p2);
+        e.apply(Event::NoteOn {
+            ch: 1,
+            note: 72,
+            vel: 100,
+        });
+        e.render(&p2);
+        assert_eq!(e.active_voices(), 2);
+    }
+
+    #[test]
+    fn master_chain_runs_on_the_mix() {
+        // post gain x2 should double the output of a plain saw
+        let plain = compile(&grid_from(".A\n.!"));
+        let gained = compile(&grid_from(".A\n.!\n9G"));
+        let mut a = Engine::new(1, 48000.0);
+        let mut b = Engine::new(1, 48000.0);
+        a.apply(Event::NoteOn {
+            ch: 0,
+            note: 60,
+            vel: 64,
+        });
+        b.apply(Event::NoteOn {
+            ch: 0,
+            note: 60,
+            vel: 64,
+        });
+        let ya = a.render(&plain)[0].atanh();
+        let yb = b.render(&gained)[0].atanh();
+        assert!((yb - 2.0 * ya).abs() < 1e-4);
     }
 }

src/grid.rs

@@ -18,7 +18,11 @@ pub struct Grid {
 
 impl Grid {
     pub fn new() -> Self {
-        Grid { w: DEFAULT_W, h: DEFAULT_H, cells: vec!['.'; SLOTS] }
+        Grid {
+            w: DEFAULT_W,
+            h: DEFAULT_H,
+            cells: vec!['.'; SLOTS],
+        }
     }
 
     #[inline]
@@ -41,15 +45,58 @@ impl Grid {
         self.h = nh.clamp(1, MAX_H);
         self.w = nw.clamp(1, MAX_W);
     }
+
+    /// Plain-text patch format: one line per row, `.` for an empty cell.
+    pub fn to_text(&self) -> String {
+        let mut s = String::with_capacity((self.w + 1) * self.h);
+        for row in 0..self.h {
+            for col in 0..self.w {
+                s.push(self.get(col, row));
+            }
+            s.push('\n');
+        }
+        s
+    }
+
+    /// Parse the text format; the grid takes the text's size (clamped).
+    pub fn from_text(text: &str) -> Self {
+        let lines: Vec<&str> = text.lines().filter(|l| !l.starts_with('#')).collect();
+        let h = lines.len().clamp(1, MAX_H);
+        let w = lines
+            .iter()
+            .map(|l| l.chars().count())
+            .max()
+            .unwrap_or(1)
+            .clamp(1, MAX_W);
+        let mut g = Grid {
+            w,
+            h,
+            cells: vec!['.'; SLOTS],
+        };
+        for (r, line) in lines.iter().enumerate().take(h) {
+            for (c, ch) in line.chars().enumerate().take(w) {
+                g.set(c, r, if ch == ' ' { '.' } else { ch });
+            }
+        }
+        g
+    }
 }
 
 /// orca-c's ruler snap: resize by one ruler division, snapped to a
 /// ruler-aligned size (1, 9, 17, ...) rather than a plain +/-1.
 pub fn ruler_snap(size: usize, delta_rulers: isize) -> usize {
     if size == 0 {
-        return if delta_rulers > 0 { RULER * delta_rulers as usize } else { 1 };
+        return if delta_rulers > 0 {
+            RULER * delta_rulers as usize
+        } else {
+            1
+        };
     }
-    let size = if delta_rulers < 0 { size + RULER - 1 } else { size };
+    let size = if delta_rulers < 0 {
+        size + RULER - 1
+    } else {
+        size
+    };
     let n = ((size as isize - 1) / RULER as isize + delta_rulers).max(0);
     (RULER as isize * n + 1) as usize
 }
@@ -82,6 +129,23 @@ mod tests {
         assert_eq!(g.get(g.w, 0), '.'); // just past the right edge
     }
 
+    #[test]
+    fn text_roundtrip() {
+        let mut g = Grid::new();
+        g.resize(3, 4);
+        g.set(1, 0, 'O');
+        g.set(1, 2, '!');
+        let t = g.to_text();
+        assert_eq!(t, ".O..\n....\n.!..\n");
+        let g2 = Grid::from_text(&t);
+        assert_eq!((g2.w, g2.h), (4, 3));
+        assert_eq!(g2.get(1, 2), '!');
+        // spaces read as empty, comment lines are skipped
+        let g3 = Grid::from_text("# patch\nA \n!.\n");
+        assert_eq!((g3.w, g3.h), (2, 2));
+        assert_eq!(g3.get(1, 0), '.');
+    }
+
     #[test]
     fn set_get_roundtrip_and_resize_preserves() {
         let mut g = Grid::new();

src/main.rs

@@ -1,17 +1,21 @@
 //! galdr - a terminal grid synthesizer.
 //!
 //! Signal flows downward through single-glyph unit generators; each MIDI note
-//! voices the whole grid; the mix is rendered low-latency to PipeWire. Pairs
-//! with orca (MIDI/OSC/UDP out) and spectrust (visualize the output).
+//! voices the whole grid (or the columns tagged with its channel); the mix is
+//! rendered low-latency to PipeWire. Pairs with orca (MIDI + UDP out) and
+//! spectrust (visualize the output).
 
 mod audio;
 mod dsp;
 mod engine;
 mod grid;
 mod midi;
+mod patch;
 mod tui;
+mod udp;
 
-use std::sync::atomic::AtomicU32;
+use std::path::PathBuf;
+use std::sync::atomic::{AtomicBool, AtomicU32};
 use std::sync::Arc;
 
 use arc_swap::ArcSwap;
@@ -22,32 +26,54 @@ use crate::grid::Grid;
 const HELP: &str = "\
 galdr - terminal grid synthesizer
 
-Usage: galdr [options]
+Usage: galdr [options] [patch.galdr]
 
 Options:
     --latency <frames>  PipeWire quantum; lower = lower latency (default: 256)
     --poly <n>          Number of voices (default: 8)
     --rate <hz>         Sample rate (default: 48000)
+    --stems <n>         Add n mono PipeWire nodes galdr.ch0..galdr.ch<n-1>, one per
+                        channel tag, carrying that channel's dry sum (default: 0)
+    --udp <port>        Listen for orca's `;` UDP strings (default: 49161;
+                        0 disables)
+    --patches <dir>     Patch directory for `#name` loads and dated saves
+                        (default: ~/hometaping)
     --midi-name <s>     Connect to the input port matching <s> instead of
                         creating the virtual 'galdr' port
     -h, --help          Print this message
 
-Grid glyphs are UPPERCASE operators; digits 0-9 are constants; lowercase a-z
-read MIDI CC (a = CC 0). Signal flows down (input = the cell above); the left
-and right neighbours are params.
-    sources   O sine   A saw   U pulse   V tri   N noise   (ratio/width <- left)
+Grid glyphs are UPPERCASE operators. Signal flows down (input = the cell
+above); the left and right neighbours are params: digit 0-9 constant, a-z a
+register (MIDI CC a = 0, or UDP), @ velocity, ^ key tracking, ? per-note random.
+A base-36 glyph above a column's top operator tags the column with a MIDI
+channel (0-9 a-f = 1-16); untagged columns play every channel. A '>' right of
+the tag makes the channel mono-legato: overlapping notes slide (60 ms).
+    sources   O sine  A saw  U pulse  V tri  N noise  X FM (mod <- left cell, index <- right)
     filters   L lowpass  H highpass  B bandpass   (cutoff <- left, resonance <- right)
     shapers   S soft/tanh(drive<-left)  C clip(<-left)  F fold(<-left)  D decimate(<-left)
     amp/mod   E envelope(atk<-left, rel<-right)  G gain(<-left)  R ringmod(ratio<-left)
+    control   K decay envelope (decay<-left, floor<-right): put it LEFT of an operator
+              and it drives that operator's left param (2KL5 = 303 filter sweep)
     routing   M mix (adds the cell to its left)   ! output to master
+    master    operators BELOW a ! process the stereo master in series:
+              Z delay(time<-left, fb<-right)  W chorus(rate<-left, depth<-right) + filters/shapers
+UDP commands (one or more per datagram, split on whitespace/';'):
+    k7  set register k to 7/35      *3  bang column 3 (5 ms gate, no note)
+    @34O  write O at column 3, row 4      #verse  load <patches>/verse.galdr
+
+With no patch file, galdr opens ~/hometaping/<date>.galdr if it exists and
+Ctrl+S writes it (the same dated naming as the orca files kept there).
 ";
 
 fn main() -> anyhow::Result<()> {
     let mut latency: u32 = 256;
     let mut poly: usize = 8;
     let mut rate: u32 = 48000;
-    let channels: u8 = 2;
+    let mut stems: usize = 0;
+    let mut udp_port: u16 = 49161;
+    let mut patches: Option<PathBuf> = None;
     let mut midi_name: Option<String> = None;
+    let mut file: Option<PathBuf> = None;
 
     let mut args = std::env::args().skip(1);
     while let Some(a) = args.next() {
@@ -55,20 +81,137 @@ fn main() -> anyhow::Result<()> {
             "--latency" => latency = args.next().and_then(|v| v.parse().ok()).unwrap_or(latency),
             "--poly" => poly = args.next().and_then(|v| v.parse().ok()).unwrap_or(poly),
             "--rate" => rate = args.next().and_then(|v| v.parse().ok()).unwrap_or(rate),
+            "--stems" => stems = args.next().and_then(|v| v.parse().ok()).unwrap_or(stems),
+            "--udp" => udp_port = args.next().and_then(|v| v.parse().ok()).unwrap_or(udp_port),
+            "--patches" => patches = args.next().map(PathBuf::from),
             "--midi-name" => midi_name = args.next(),
             "-h" | "--help" => {
                 print!("{HELP}");
                 return Ok(());
             }
+            other if !other.starts_with('-') && file.is_none() => file = Some(PathBuf::from(other)),
             other => {
                 eprintln!("unknown option: {other}\n\n{HELP}");
                 std::process::exit(2);
             }
         }
     }
+    let stems = stems.min(engine::CHANNELS);
+    let patches = patches.unwrap_or_else(patch::default_dir);
 
-    // A default patch so the first run makes sound: a plain sine->env voice and
-    // a filtered saw voice.
+    // No file: today's patch (~/hometaping/<date>.galdr) if it exists, so the
+    // session continues where it left off and Ctrl+S keeps writing it.
+    if file.is_none() {
+        let today = patch::dated(&patches, &patch::today());
+        if today.exists() {
+            file = Some(today);
+        }
+    }
+    let grid = match &file {
+        Some(p) if p.exists() => patch::load(p)?,
+        _ => default_grid(),
+    };
+
+    let prog = Arc::new(ArcSwap::from_pointee(compile(&grid)));
+    let voices = Arc::new(AtomicU32::new(0));
+    let connected = Arc::new(AtomicBool::new(false));
+
+    // The audio thread drains one lock-free ring. MIDI (a midir callback) and
+    // UDP (its own thread) are separate producers, so each gets its own ring
+    // and a small pump thread merges them; no callback ever blocks.
+    let (prod_ev, cons_ev) = rtrb::RingBuffer::new(1024);
+    let (prod_midi, cons_midi) = rtrb::RingBuffer::new(1024);
+    let (prod_udp, cons_udp) = rtrb::RingBuffer::new(1024);
+    let (ctrl_tx, ctrl_rx) = std::sync::mpsc::channel();
+
+    audio::spawn(
+        prog.clone(),
+        cons_ev,
+        voices.clone(),
+        connected.clone(),
+        audio::Config {
+            sr: rate,
+            latency,
+            poly,
+            stems,
+        },
+    )
+    .map_err(|e| anyhow::anyhow!("audio: {e}"))?;
+    spawn_pump(prod_ev, vec![cons_midi, cons_udp])?;
+
+    // Keep the MIDI connection alive for the program's lifetime.
+    let _midi = match midi::connect(prod_midi, midi_name) {
+        Ok(conn) => Some(conn),
+        Err(e) => {
+            eprintln!("warning: MIDI unavailable ({e}); running without note input");
+            None
+        }
+    };
+
+    let udp = if udp_port > 0 {
+        match udp::spawn(udp_port, prod_udp, ctrl_tx) {
+            Ok(()) => Some(udp_port),
+            Err(e) => {
+                eprintln!("warning: UDP unavailable ({e}); running without orca control");
+                None
+            }
+        }
+    } else {
+        None
+    };
+
+    tui::run(
+        tui::Session {
+            prog,
+            voices,
+            connected,
+            latency,
+            ctrl: ctrl_rx,
+            patches,
+            file,
+            udp_port: udp,
+        },
+        grid,
+    )?;
+    Ok(())
+}
+
+fn spawn_pump(
+    mut out: rtrb::Producer<engine::Event>,
+    mut inputs: Vec<rtrb::Consumer<engine::Event>>,
+) -> std::io::Result<()> {
+    // GALDR_DEBUG=<file> appends every event that reaches the engine.
+    let mut log = std::env::var_os("GALDR_DEBUG").and_then(|p| {
+        std::fs::OpenOptions::new()
+            .create(true)
+            .append(true)
+            .open(p)
+            .ok()
+    });
+    std::thread::Builder::new()
+        .name("galdr-pump".into())
+        .spawn(move || loop {
+            let mut idle = true;
+            for c in inputs.iter_mut() {
+                while let Ok(ev) = c.pop() {
+                    if let Some(f) = log.as_mut() {
+                        use std::io::Write;
+                        let _ = writeln!(f, "{ev:?}");
+                    }
+                    let _ = out.push(ev);
+                    idle = false;
+                }
+            }
+            if idle {
+                std::thread::sleep(std::time::Duration::from_micros(500));
+            }
+        })?;
+    Ok(())
+}
+
+/// A default patch so the first run makes sound: a plain sine->env voice and
+/// a filtered saw voice.
+fn default_grid() -> Grid {
     let mut grid = Grid::new();
     grid.set(0, 0, 'O'); // sine
     grid.set(0, 1, 'E'); // -> envelope
@@ -78,24 +221,5 @@ fn main() -> anyhow::Result<()> {
     grid.set(2, 1, 'L'); // -> lowpass
     grid.set(2, 2, 'E'); // -> envelope
     grid.set(2, 3, '!'); // -> out
-
-    let prog = Arc::new(ArcSwap::from_pointee(compile(&grid)));
-    let voices = Arc::new(AtomicU32::new(0));
-
-    let (prod_ev, cons_ev) = rtrb::RingBuffer::new(1024);
-
-    audio::spawn(prog.clone(), cons_ev, voices.clone(), rate, channels, latency, poly)
-        .map_err(|e| anyhow::anyhow!("audio: {e}"))?;
-
-    // Keep the MIDI connection alive for the program's lifetime.
-    let _midi = match midi::connect(prod_ev, midi_name) {
-        Ok(conn) => Some(conn),
-        Err(e) => {
-            eprintln!("warning: MIDI unavailable ({e}); running without note input");
-            None
-        }
-    };
-
-    tui::run(prog, voices, grid, latency)?;
-    Ok(())
+    grid
 }

src/midi.rs

@@ -1,5 +1,6 @@
 //! MIDI input. galdr owns a virtual input port named "galdr" (symmetric with
 //! orca's virtual output), so orca or any client connects to it in the graph.
+//! The channel nibble is kept: tagged columns voice only their channel.
 
 use anyhow::{anyhow, Result};
 use midir::os::unix::VirtualInput;
@@ -8,34 +9,85 @@ use rtrb::Producer;
 
 use crate::engine::Event;
 
-pub fn connect(prod: Producer<Event>, port_name: Option<String>) -> Result<MidiInputConnection<Producer<Event>>> {
+/// Decode one MIDI message into an engine event.
+pub fn decode(msg: &[u8]) -> Option<Event> {
+    if msg.len() < 3 {
+        return None;
+    }
+    let ch = msg[0] & 0x0F;
+    match msg[0] & 0xF0 {
+        0x90 if msg[2] > 0 => Some(Event::NoteOn {
+            ch,
+            note: msg[1],
+            vel: msg[2],
+        }),
+        0x80 | 0x90 => Some(Event::NoteOff { ch, note: msg[1] }), // note-on velocity 0
+        0xB0 => Some(Event::Cc {
+            idx: msg[1],
+            val: msg[2],
+        }),
+        _ => None,
+    }
+}
+
+pub fn connect(
+    prod: Producer<Event>,
+    port_name: Option<String>,
+) -> Result<MidiInputConnection<Producer<Event>>> {
     let mut input = MidiInput::new("galdr").map_err(|e| anyhow!("MIDI init: {e}"))?;
     input.ignore(midir::Ignore::None);
 
     let cb = move |_stamp: u64, msg: &[u8], prod: &mut Producer<Event>| {
-        if msg.len() < 2 {
-            return;
+        if let Some(ev) = decode(msg) {
+            let _ = prod.push(ev);
         }
-        let status = msg[0] & 0xF0;
-        let ev = match status {
-            0x90 if msg[2] > 0 => Event::NoteOn { note: msg[1], vel: msg[2] },
-            0x80 => Event::NoteOff { note: msg[1] },
-            0x90 => Event::NoteOff { note: msg[1] }, // note-on velocity 0
-            0xB0 => Event::Cc { idx: msg[1], val: msg[2] },
-            _ => return,
-        };
-        let _ = prod.push(ev);
     };
 
     if let Some(name) = port_name {
         let ports = input.ports();
         let port = ports
             .iter()
-            .find(|p| input.port_name(p).map(|n| n.contains(&name)).unwrap_or(false))
+            .find(|p| {
+                input
+                    .port_name(p)
+                    .map(|n| n.contains(&name))
+                    .unwrap_or(false)
+            })
             .cloned()
             .ok_or_else(|| anyhow!("no MIDI input port matching {name:?}"))?;
-        input.connect(&port, "galdr-in", cb, prod).map_err(|e| anyhow!("MIDI connect: {e}"))
+        input
+            .connect(&port, "galdr-in", cb, prod)
+            .map_err(|e| anyhow!("MIDI connect: {e}"))
     } else {
-        input.create_virtual("galdr", cb, prod).map_err(|e| anyhow!("create virtual MIDI port: {e}"))
+        input
+            .create_virtual("galdr", cb, prod)
+            .map_err(|e| anyhow!("create virtual MIDI port: {e}"))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn decode_keeps_channel() {
+        assert_eq!(
+            decode(&[0x92, 60, 100]),
+            Some(Event::NoteOn {
+                ch: 2,
+                note: 60,
+                vel: 100
+            })
+        );
+        assert_eq!(
+            decode(&[0x8F, 60, 0]),
+            Some(Event::NoteOff { ch: 15, note: 60 })
+        );
+        assert_eq!(
+            decode(&[0x90, 60, 0]),
+            Some(Event::NoteOff { ch: 0, note: 60 })
+        );
+        assert_eq!(decode(&[0xB3, 7, 64]), Some(Event::Cc { idx: 7, val: 64 }));
+        assert_eq!(decode(&[0xF8]), None);
     }
 }

src/patch.rs

@@ -0,0 +1,293 @@
+//! Patch files: the grid's text format on disk. `galdr <file>` opens one,
+//! Ctrl+S writes it back, and `#name` over UDP loads `<patches dir>/name.galdr`.
+//!
+//! With no file given, galdr works on today's patch, `~/hometaping/<date>.galdr`
+//! (`date -I` form), next to the orca files kept the same way: starting galdr
+//! opens it if it exists and Ctrl+S writes it.
+
+use std::path::{Path, PathBuf};
+
+use anyhow::{Context, Result};
+
+use crate::grid::Grid;
+
+pub const EXT: &str = "galdr";
+
+/// The patches directory: `~/hometaping`, where the dated orca files live.
+pub fn default_dir() -> PathBuf {
+    std::env::var_os("HOME")
+        .map(PathBuf::from)
+        .unwrap_or_else(|| PathBuf::from("."))
+        .join("hometaping")
+}
+
+/// Today's date as `date -I` prints it (local time), with a UTC fallback.
+pub fn today() -> String {
+    if let Ok(out) = std::process::Command::new("date").arg("-I").output() {
+        if out.status.success() {
+            let s = String::from_utf8_lossy(&out.stdout).trim().to_string();
+            if s.len() == 10 {
+                return s;
+            }
+        }
+    }
+    let secs = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .map(|d| d.as_secs())
+        .unwrap_or(0);
+    civil_from_days((secs / 86400) as i64)
+}
+
+/// Howard Hinnant's days-since-epoch to YYYY-MM-DD.
+fn civil_from_days(z: i64) -> String {
+    let z = z + 719468;
+    let era = if z >= 0 { z } else { z - 146096 } / 146097;
+    let doe = z - era * 146097;
+    let yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
+    let y = yoe + era * 400;
+    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
+    let mp = (5 * doy + 2) / 153;
+    let d = doy - (153 * mp + 2) / 5 + 1;
+    let m = if mp < 10 { mp + 3 } else { mp - 9 };
+    let y = if m <= 2 { y + 1 } else { y };
+    format!("{y:04}-{m:02}-{d:02}")
+}
+
+/// `<dir>/<date>.galdr`: the patch Ctrl+S writes when no file was given.
+pub fn dated(dir: &Path, date: &str) -> PathBuf {
+    dir.join(format!("{date}.{EXT}"))
+}
+
+/// Resolve a UDP patch name inside the patches directory (no path escapes:
+/// the parser already restricts names to alphanumerics, `-` and `_`).
+/// `.galdr` is the name; a legacy `.txt` is accepted if that is what exists.
+pub fn named(dir: &Path, name: &str) -> PathBuf {
+    let p = dir.join(format!("{name}.{EXT}"));
+    if p.exists() {
+        return p;
+    }
+    let legacy = dir.join(format!("{name}.txt"));
+    if legacy.exists() {
+        legacy
+    } else {
+        p
+    }
+}
+
+pub fn load(path: &Path) -> Result<Grid> {
+    let text = std::fs::read_to_string(path).with_context(|| format!("read {}", path.display()))?;
+    Ok(Grid::from_text(&text))
+}
+
+pub fn save(path: &Path, grid: &Grid) -> Result<()> {
+    if let Some(parent) = path.parent() {
+        std::fs::create_dir_all(parent).with_context(|| format!("create {}", parent.display()))?;
+    }
+    std::fs::write(path, grid.to_text()).with_context(|| format!("write {}", path.display()))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn dated_path_matches_orca_convention() {
+        let p = dated(Path::new("/home/x/hometaping"), "2026-10-08");
+        assert_eq!(p, PathBuf::from("/home/x/hometaping/2026-10-08.galdr"));
+        assert_eq!(civil_from_days(0), "1970-01-01");
+        assert_eq!(civil_from_days(20734), "2026-10-08");
+        assert_eq!(today().len(), 10);
+    }
+
+    #[test]
+    fn named_prefers_galdr_then_legacy_txt() {
+        let dir = std::env::temp_dir().join(format!("galdr-named-test-{}", std::process::id()));
+        std::fs::create_dir_all(&dir).unwrap();
+        assert_eq!(named(&dir, "x"), dir.join("x.galdr"));
+        std::fs::write(dir.join("y.txt"), "A\n!\n").unwrap();
+        assert_eq!(named(&dir, "y"), dir.join("y.txt"));
+        std::fs::write(dir.join("y.galdr"), "A\n!\n").unwrap();
+        assert_eq!(named(&dir, "y"), dir.join("y.galdr"));
+        let _ = std::fs::remove_dir_all(dir);
+    }
+
+    #[test]
+    fn save_and_load_roundtrip() {
+        let dir = std::env::temp_dir().join(format!("galdr-patch-test-{}", std::process::id()));
+        let path = named(&dir, "verse");
+        let mut g = Grid::new();
+        g.resize(2, 3);
+        g.set(0, 0, 'A');
+        g.set(0, 1, '!');
+        save(&path, &g).unwrap();
+        let g2 = load(&path).unwrap();
+        assert_eq!((g2.w, g2.h), (3, 2));
+        assert_eq!(g2.get(0, 1), '!');
+        let _ = std::fs::remove_dir_all(dir);
+    }
+}
+#[cfg(test)]
+mod example_render {
+    use super::*;
+    use crate::dsp::compile;
+    use crate::engine::{Engine, Event};
+    #[test]
+    fn drums_example_each_channel_sounds() {
+        let g = load(std::path::Path::new("examples/drums.galdr")).unwrap();
+        let p = compile(&g);
+        for (ch, note, name) in [
+            (0u8, 36u8, "bass"),
+            (9, 36, "kick"),
+            (10, 50, "snare"),
+            (11, 65, "hats"),
+        ] {
+            let mut e = Engine::new(8, 48000.0);
+            e.apply(Event::NoteOn { ch, note, vel: 110 });
+            let mut peak = 0f32;
+            let mut early = 0f32;
+            let mut late = 0f32;
+            let mut zc_early = 0;
+            let mut zc_late = 0;
+            let mut prev = 0f32;
+            for i in 0..24000 {
+                let y = e.render(&p)[0];
+                peak = peak.max(y.abs());
+                if i < 2400 {
+                    early = early.max(y.abs());
+                    if (y < 0.0) != (prev < 0.0) {
+                        zc_early += 1;
+                    }
+                }
+                if (12000..14400).contains(&i) {
+                    late = late.max(y.abs());
+                    if (y < 0.0) != (prev < 0.0) {
+                        zc_late += 1;
+                    }
+                }
+                prev = y;
+                if i == 4800 {
+                    e.apply(Event::NoteOff { ch, note });
+                }
+            }
+            eprintln!("{name:5} peak {peak:.2} first50ms {early:.2} (zc {zc_early}) at250ms {late:.2} (zc {zc_late}) voices {}", e.active_voices());
+            assert!(peak > 0.05 && peak <= 1.0, "{name} silent or clipping");
+            let mut e2 = Engine::new(8, 48000.0);
+            e2.apply(Event::NoteOn {
+                ch: 5,
+                note,
+                vel: 110,
+            });
+            assert!(
+                (0..1000)
+                    .map(|_| e2.render(&p)[0].abs())
+                    .fold(0f32, f32::max)
+                    == 0.0,
+                "{name} leaks onto channel 6"
+            );
+        }
+    }
+}
+
+#[cfg(test)]
+mod orchestra_example {
+    use super::*;
+    use crate::dsp::compile;
+    use crate::engine::{Engine, Event};
+
+    #[test]
+    fn each_section_sounds_and_stays_on_its_channel() {
+        let g = load(std::path::Path::new("examples/orchestra.galdr")).unwrap();
+        let p = compile(&g);
+        assert_eq!(p.post.len(), 1, "one master chain (hall) expected");
+        assert_eq!(p.post[0].len(), 3, "highpass, chorus, delay");
+        let names = [
+            "strings",
+            "low strings",
+            "brass",
+            "horns",
+            "flute",
+            "reed",
+            "clarinet",
+            "timpani",
+            "harp",
+            "choir",
+        ];
+        for (ch, name) in names.iter().enumerate() {
+            let note = if ch == 7 { 36 } else { 60 };
+            let mut e = Engine::new(8, 48000.0);
+            e.apply(Event::Reg {
+                idx: b'k' - b'a',
+                val: 0.5,
+            });
+            e.apply(Event::NoteOn {
+                ch: ch as u8,
+                note,
+                vel: 100,
+            });
+            let mut peak = 0f32;
+            for i in 0..48000 {
+                peak = peak.max(e.render(&p)[0].abs());
+                if i == 24000 {
+                    e.apply(Event::NoteOff { ch: ch as u8, note });
+                }
+            }
+            eprintln!("{name:12} peak {peak:.2}");
+            assert!(peak > 0.03 && peak <= 1.0, "{name} silent or clipping");
+            let mut e2 = Engine::new(8, 48000.0);
+            e2.apply(Event::NoteOn {
+                ch: 12,
+                note,
+                vel: 100,
+            });
+            assert!(
+                (0..2000)
+                    .map(|_| e2.render(&p)[0].abs())
+                    .fold(0f32, f32::max)
+                    == 0.0,
+                "{name} leaks onto channel 13"
+            );
+        }
+    }
+}
+
+#[cfg(test)]
+mod acid_example {
+    use super::*;
+    use crate::dsp::compile;
+    use crate::engine::{Engine, Event};
+
+    #[test]
+    fn acid_line_sweeps_and_slides() {
+        let g = load(std::path::Path::new("examples/acid.galdr")).unwrap();
+        let p = compile(&g);
+        assert!(p.legato[0], "channel 1 slides");
+        let mut e = Engine::new(8, 48000.0);
+        e.apply(Event::NoteOn {
+            ch: 0,
+            note: 36,
+            vel: 127,
+        });
+        let hf =
+            |x: &[f32]| x.windows(2).map(|w| (w[1] - w[0]).abs()).sum::<f32>() / x.len() as f32;
+        let early: Vec<f32> = (0..2000).map(|_| e.render(&p)[0]).collect();
+        for _ in 0..12000 {
+            e.render(&p);
+        }
+        let late: Vec<f32> = (0..2000).map(|_| e.render(&p)[0]).collect();
+        assert!(
+            early.iter().fold(0f32, |a, b| a.max(b.abs())) > 0.1,
+            "audible"
+        );
+        assert!(
+            hf(&early) > 1.5 * hf(&late),
+            "filter sweeps down over the note"
+        );
+        e.apply(Event::NoteOn {
+            ch: 0,
+            note: 48,
+            vel: 127,
+        }); // overlapping -> slide, one voice
+        e.render(&p);
+        assert_eq!(e.active_voices(), 1);
+    }
+}

src/tui.rs

@@ -5,9 +5,11 @@
 //! a detailed help overlay; run a spectrum analyzer on the side if you want one.
 
 use std::io::{self, Write};
-use std::sync::atomic::{AtomicU32, Ordering};
+use std::path::PathBuf;
+use std::sync::atomic::{AtomicBool, AtomicU32, Ordering};
+use std::sync::mpsc::Receiver;
 use std::sync::Arc;
-use std::time::Duration;
+use std::time::{Duration, Instant};
 
 use arc_swap::ArcSwap;
 use crossterm::cursor::{Hide, MoveTo, Show};
@@ -20,26 +22,32 @@ use crossterm::{execute, queue, terminal};
 
 use crate::dsp::{compile, Program};
 use crate::grid::{ruler_snap, Grid, RULER};
+use crate::patch;
+use crate::udp::Control;
 
 const HELP: &[&str] = &[
     "galdr — grid synthesizer",
     "",
     "Signal flows DOWN: a cell's input is the cell above it. Operators are",
-    "UPPERCASE. A digit 0-9 to the left/right is a constant param; a lowercase",
-    "a-z reads MIDI CC (a = CC 0). Every note plays the whole grid; each ! sums",
-    "into the master, so parallel columns stack voices/timbres.",
+    "UPPERCASE. Left/right neighbours are params: digit 0-9 constant, a-z a",
+    "register (MIDI CC a=0, or UDP), @ velocity, ^ key tracking, ? per-note random.",
+    "A base-36 glyph ABOVE a column's top operator tags it with a MIDI channel",
+    "(0-9 a-f = ch 1-16); untagged columns play every channel. Each ! sums into",
+    "the master; operators BELOW a ! form the master chain (stereo, serial).",
     "",
-    "SOURCES   O sine   A saw   U pulse   V triangle   N noise",
-    "          left param = pitch ratio (O/A) or pulse width (U)",
-    "FILTERS   L lowpass   H highpass   B bandpass   (state-variable)",
-    "          left = cutoff, right = resonance (higher glyph = more)",
-    "SHAPERS   S soft clip/tanh (left=drive)   C hard clip (left=threshold)",
-    "          F wavefolder (left=amount)      D decimate/bitcrush (left=rate)",
-    "AMP/MOD   E envelope, note-gated (left=attack, right=release)",
-    "          G gain (left=amount)            R ring modulator (left=ratio)",
+    "SOURCES   O sine   A saw   U pulse   V triangle   N noise   X FM (mod <- LEFT",
+    "          cell + above, index <- right)   left = pitch ratio (O/A) / width (U)",
+    "FILTERS   L lowpass   H highpass   B bandpass   left = cutoff, right = resonance",
+    "SHAPERS   S soft clip (left=drive)  C clip (left)  F fold (left)  D decimate (left)",
+    "AMP/MOD   E envelope (left=attack, right=release)   G gain   R ring mod (ratio)",
+    "CONTROL   K decay envelope (left=decay, right=floor); LEFT of an operator it drives",
+    "          that operator's left param: 2KL5 = filter sweep. tag> = slide (legato channel)",
     "ROUTING   M mix — adds the cell to its LEFT      ! output to master",
+    "MASTER    Z delay (left=time, right=feedback)   W chorus (left=rate, right=depth)",
+    "          + any filter/shaper, placed below a !",
+    "UDP       k7 reg k=7/35 · *3 bang column 3 · @34O write O at col 3,row 4 · #name load",
     "",
-    "KEYS      arrows move · type a glyph to place · Backspace clears",
+    "KEYS      arrows move · type a glyph · Backspace clears · Ctrl+S save patch",
     "          ( ) width -/+   _ + height -/+   Ctrl+arrows resize by one",
     "          ? toggle this help · Esc quit",
 ];
@@ -52,17 +60,30 @@ enum Cs {
 
 fn glyph_color(c: char) -> Color {
     match c {
-        'O' | 'A' | 'U' | 'V' | 'N' => Color::Cyan,
+        'O' | 'A' | 'U' | 'V' | 'N' | 'X' => Color::Cyan,
         'L' | 'H' | 'B' => Color::Blue,
         'S' | 'C' | 'F' | 'D' => Color::Yellow,
-        'E' | 'G' | 'R' | 'M' => Color::Green,
+        'E' | 'G' | 'R' | 'M' | 'Z' | 'W' | 'K' => Color::Green,
         '!' => Color::Magenta,
         '0'..='9' => Color::Grey,
         'a'..='z' => Color::DarkYellow,
+        '@' | '^' | '?' => Color::Red,
         _ => Color::White,
     }
 }
 
+/// Everything the editor needs besides the grid itself.
+pub struct Session {
+    pub prog: Arc<ArcSwap<Program>>,
+    pub voices: Arc<AtomicU32>,
+    pub connected: Arc<AtomicBool>,
+    pub latency: u32,
+    pub ctrl: Receiver<Control>,
+    pub patches: PathBuf,
+    pub file: Option<PathBuf>,
+    pub udp_port: Option<u16>,
+}
+
 struct Renderer {
     cells: Vec<(char, Cs)>,
     status: String,
@@ -89,26 +110,70 @@ impl Renderer {
     }
 }
 
-pub fn run(
-    prog: Arc<ArcSwap<Program>>,
-    voices: Arc<AtomicU32>,
-    mut grid: Grid,
-    latency: u32,
-) -> io::Result<()> {
+pub fn run(mut s: Session, mut grid: Grid) -> io::Result<()> {
     enable_raw_mode()?;
     let mut out = io::stdout();
     execute!(out, EnterAlternateScreen, Hide)?;
     let (mut cx, mut cy) = (0usize, 0usize);
     let mut help = false;
     let mut r = Renderer::new();
+    let mut note: Option<(String, Instant)> = None;
+    let set_note =
+        |note: &mut Option<(String, Instant)>, msg: String| *note = Some((msg, Instant::now()));
 
     let res = (|| -> io::Result<()> {
         loop {
-            draw(&mut out, &grid, cx, cy, voices.load(Ordering::Relaxed), latency, help, &mut r)?;
+            if note
+                .as_ref()
+                .is_some_and(|(_, t)| t.elapsed() > Duration::from_secs(4))
+            {
+                note = None;
+            }
+            let status = status_line(
+                &s,
+                &grid,
+                s.voices.load(Ordering::Relaxed),
+                note.as_ref().map(|(m, _)| m.as_str()),
+            );
+            draw(&mut out, &grid, cx, cy, &status, help, &mut r)?;
+
+            // Edits arriving over UDP (orca patching the grid, patch loads).
+            let mut remote = false;
+            while let Ok(c) = s.ctrl.try_recv() {
+                match c {
+                    Control::Set { col, row, glyph } => {
+                        if col < grid.w && row < grid.h {
+                            grid.set(col, row, if glyph == ' ' { '.' } else { glyph });
+                            remote = true;
+                        }
+                    }
+                    Control::Load(name) => {
+                        let path = patch::named(&s.patches, &name);
+                        match patch::load(&path) {
+                            Ok(g) => {
+                                grid = g;
+                                s.file = Some(path);
+                                remote = true;
+                                set_note(&mut note, format!("loaded {name}"));
+                            }
+                            Err(e) => set_note(&mut note, format!("load {name}: {e}")),
+                        }
+                    }
+                }
+            }
+            if remote {
+                cx = cx.min(grid.w - 1);
+                cy = cy.min(grid.h - 1);
+                s.prog.store(Arc::new(compile(&grid)));
+                r.init = false; // size may have changed: repaint fully
+            }
+
             if !event::poll(Duration::from_millis(33))? {
                 continue;
             }
-            let Event::Key(k) = event::read()? else { continue };
+            let Event::Key(k) = event::read()? else {
+                continue;
+            };
             if k.kind != KeyEventKind::Press {
                 continue;
             }
@@ -124,6 +189,20 @@ pub fn run(
                     }
                 }
                 KeyCode::Char('c') if ctrl => return Ok(()),
+                KeyCode::Char('s') if ctrl => {
+                    // No file given: today's patch next to the orca files.
+                    let path = s
+                        .file
+                        .clone()
+                        .unwrap_or_else(|| patch::dated(&s.patches, &patch::today()));
+                    match patch::save(&path, &grid) {
+                        Ok(()) => {
+                            set_note(&mut note, format!("saved {}", path.display()));
+                            s.file = Some(path);
+                        }
+                        Err(e) => set_note(&mut note, format!("save failed: {e}")),
+                    }
+                }
                 KeyCode::Char('?') => help = !help,
                 _ if help => {}
                 KeyCode::Char('(') => {
@@ -169,7 +248,6 @@ pub fn run(
                 KeyCode::Char(c) => {
                     grid.set(cx, cy, if c == ' ' { '.' } else { c });
                     edited = true;
-                    cx = (cx + 1).min(grid.w - 1);
                 }
                 _ => {}
             }
@@ -178,7 +256,7 @@ pub fn run(
                 cy = cy.min(grid.h - 1);
             }
             if resized || edited {
-                prog.store(Arc::new(compile(&grid)));
+                s.prog.store(Arc::new(compile(&grid)));
             }
         }
     })();
@@ -188,25 +266,45 @@ pub fn run(
     res
 }
 
-#[allow(clippy::too_many_arguments)]
+fn status_line(s: &Session, grid: &Grid, voices: u32, note: Option<&str>) -> String {
+    let file = s
+        .file
+        .as_ref()
+        .and_then(|p| p.file_name())
+        .map(|f| f.to_string_lossy().into_owned())
+        .unwrap_or_else(|| "(unsaved)".into());
+    let udp = s
+        .udp_port
+        .map(|p| format!("   udp {p}"))
+        .unwrap_or_default();
+    if !s.connected.load(Ordering::Relaxed) {
+        return format!(
+            "PIPEWIRE DOWN — reconnecting…   {}x{}   {file}",
+            grid.w, grid.h
+        );
+    }
+    match note {
+        Some(n) => format!("{n}   ·   voices {voices}   {}x{}   {file}", grid.w, grid.h),
+        None => format!(
+            "voices {voices}   {}x{}   latency {}f{udp}   {file}   ? help   Esc quit",
+            grid.w, grid.h, s.latency
+        ),
+    }
+}
+
 fn draw(
     out: &mut io::Stdout,
     grid: &Grid,
     cx: usize,
     cy: usize,
-    voices: u32,
-    latency: u32,
+    status: &str,
     help: bool,
     r: &mut Renderer,
 ) -> io::Result<()> {
     let (tw, th) = terminal::size()?;
 
-    let full = !r.init
-        || tw != r.tw
-        || th != r.th
-        || help != r.help
-        || grid.w != r.gw
-        || grid.h != r.gh;
+    let full =
+        !r.init || tw != r.tw || th != r.th || help != r.help || grid.w != r.gw || grid.h != r.gh;
     if full {
         queue!(out, Clear(ClearType::All))?;
         r.cells = vec![('\0', Cs::Fg(Color::Reset)); grid.w * grid.h];
@@ -222,7 +320,7 @@ fn draw(
     if help {
         if full {
             let oy = (th as usize).saturating_sub(HELP.len()) / 2;
-            let ox = (tw as usize).saturating_sub(74) / 2;
+            let ox = (tw as usize).saturating_sub(84) / 2;
             for (i, line) in HELP.iter().enumerate() {
                 queue!(
                     out,
@@ -243,7 +341,11 @@ fn draw(
             let raw = grid.get(col, row);
             // ruler mark on empty intersections, for orientation while sizing
             let disp = if raw == '.' {
-                if row % RULER == 0 && col % RULER == 0 { '+' } else { '.' }
+                if row % RULER == 0 && col % RULER == 0 {
+                    '+'
+                } else {
+                    '.'
+                }
             } else {
                 raw
             };
@@ -259,7 +361,11 @@ fn draw(
                 continue;
             }
             r.cells[idx] = (disp, cs);
-            queue!(out, MoveTo((off_x + col) as u16, (off_y + row) as u16), SetAttribute(Attribute::Reset))?;
+            queue!(
+                out,
+                MoveTo((off_x + col) as u16, (off_y + row) as u16),
+                SetAttribute(Attribute::Reset)
+            )?;
             match cs {
                 Cs::Cursor => queue!(out, SetAttribute(Attribute::Reverse))?,
                 Cs::Fg(color) => queue!(out, SetForegroundColor(color))?,
@@ -268,10 +374,8 @@ fn draw(
         }
     }
 
-    let status =
-        format!("voices {voices}   {}x{}   latency {latency}f   ? help   Esc quit", grid.w, grid.h);
     if status != r.status {
-        r.status = status.clone();
+        r.status = status.to_string();
         let pad: String = format!("{status:<width$}", width = tw as usize);
         queue!(
             out,

src/udp.rs

@@ -0,0 +1,170 @@
+//! UDP control from orca (`;` sends a bare string to a port). One datagram
+//! carries one or more commands separated by whitespace or `;`:
+//!
+//! * `k7`      set register k (a-z) to base-36 7 of 35   -> audio thread
+//! * `*3`      bang column 3 (base-36)                   -> audio thread
+//! * `@34O`    write glyph `O` at column 3, row 4 (base-36 each)  -> editor
+//! * `@34.`    clear that cell
+//! * `#verse`  load the patch file `verse` from the patches directory -> editor
+//!
+//! Register and bang commands go straight into the lock-free event ring the
+//! MIDI callback uses; editor commands go over a channel to the TUI thread,
+//! which owns the grid and recompiles.
+
+use std::net::UdpSocket;
+use std::sync::mpsc::Sender;
+use std::thread;
+
+use anyhow::{Context, Result};
+use rtrb::Producer;
+
+use crate::dsp::b36;
+use crate::engine::Event;
+
+/// Commands that change the grid; handled by the editor thread.
+#[derive(Clone, Debug, PartialEq)]
+pub enum Control {
+    Set { col: usize, row: usize, glyph: char },
+    Load(String),
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum Cmd {
+    Audio(Event),
+    Edit(Control),
+}
+
+pub fn parse(text: &str) -> Vec<Cmd> {
+    let mut out = Vec::new();
+    for tok in text.split(|c: char| c.is_whitespace() || c == ';') {
+        let mut it = tok.chars();
+        let Some(head) = it.next() else { continue };
+        let rest: String = it.collect();
+        match head {
+            'a'..='z' => {
+                if let Some(v) = rest.chars().next().and_then(b36) {
+                    let idx = head as u8 - b'a';
+                    out.push(Cmd::Audio(Event::Reg {
+                        idx,
+                        val: v as f32 / 35.0,
+                    }));
+                }
+            }
+            '*' => {
+                if let Some(col) = rest.chars().next().and_then(b36) {
+                    out.push(Cmd::Audio(Event::Bang { col }));
+                }
+            }
+            '@' => {
+                let mut r = rest.chars();
+                let (Some(c), Some(w), Some(g)) = (r.next(), r.next(), r.next()) else {
+                    continue;
+                };
+                if let (Some(col), Some(row)) = (b36(c), b36(w)) {
+                    out.push(Cmd::Edit(Control::Set {
+                        col: col as usize,
+                        row: row as usize,
+                        glyph: g,
+                    }));
+                }
+            }
+            '#' => {
+                let name: String = rest
+                    .chars()
+                    .filter(|c| c.is_alphanumeric() || matches!(c, '-' | '_'))
+                    .collect();
+                if !name.is_empty() {
+                    out.push(Cmd::Edit(Control::Load(name)));
+                }
+            }
+            _ => {}
+        }
+    }
+    out
+}
+
+/// Bind the socket and serve it from a background thread for the program's
+/// lifetime.
+pub fn spawn(port: u16, mut audio: Producer<Event>, editor: Sender<Control>) -> Result<()> {
+    let sock =
+        UdpSocket::bind(("0.0.0.0", port)).with_context(|| format!("bind UDP port {port}"))?;
+    thread::Builder::new()
+        .name("galdr-udp".into())
+        .spawn(move || {
+            let mut buf = [0u8; 2048];
+            while let Ok((n, _)) = sock.recv_from(&mut buf) {
+                let text = String::from_utf8_lossy(&buf[..n]);
+                for cmd in parse(&text) {
+                    match cmd {
+                        Cmd::Audio(ev) => {
+                            let _ = audio.push(ev);
+                        }
+                        Cmd::Edit(c) => {
+                            if editor.send(c).is_err() {
+                                return;
+                            }
+                        }
+                    }
+                }
+            }
+        })
+        .context("spawn UDP thread")?;
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_register_set() {
+        assert_eq!(
+            parse("k7"),
+            vec![Cmd::Audio(Event::Reg {
+                idx: 10,
+                val: 7.0 / 35.0
+            })]
+        );
+        assert_eq!(
+            parse("az"),
+            vec![Cmd::Audio(Event::Reg { idx: 0, val: 1.0 })]
+        );
+    }
+
+    #[test]
+    fn parses_bang_and_edit_and_load() {
+        assert_eq!(parse("*3"), vec![Cmd::Audio(Event::Bang { col: 3 })]);
+        assert_eq!(
+            parse("@34O"),
+            vec![Cmd::Edit(Control::Set {
+                col: 3,
+                row: 4,
+                glyph: 'O'
+            })]
+        );
+        assert_eq!(
+            parse("@a0."),
+            vec![Cmd::Edit(Control::Set {
+                col: 10,
+                row: 0,
+                glyph: '.'
+            })]
+        );
+        assert_eq!(
+            parse("#verse"),
+            vec![Cmd::Edit(Control::Load("verse".into()))]
+        );
+    }
+
+    #[test]
+    fn multiple_commands_per_datagram() {
+        let cmds = parse("k7 *2;#drop\n");
+        assert_eq!(cmds.len(), 3);
+    }
+
+    #[test]
+    fn garbage_is_ignored() {
+        assert!(parse("").is_empty());
+        assert!(parse("K7 @3 *").is_empty());
+    }
+}