Play sounds as notes of an instrument asset #331

A sound could only be played as it was, one at a time. An instrument
is a node graph that makes a note a sound: Notes nodes bring the note
in, Samples play sound assets for it, the effects of a sound FX shape
it and the Output sums the layers. Its tab plays it from a keyboard,
a behavior with Play note. It is what patterns and songs (#330) will
play.

- New asset type instrument, under the heading Music, not placeable.
  A new one starts as Notes into a Sample into the Output.
- Notes are counted as MIDI does: 60 is C4, names like C#4, sharps
  only, the lowest C-1. Notes has From and To, outputs any, note,
  frequency and velocity, and with Single notes a trigger per note,
  each with an optional name for a drum kit.
- New port type trigger, only into the trigger of a source. Inputs
  can take any number of edges now (PortDef.many): a trigger, and
  the Output, which plays everything into it side by side.
- Sample plays a sound asset. Follow note shifts it by note - root
  through the pitch worklet of #317, so it keeps its length. Gate
  fades it out at the end of the note, One-shot plays through. Loop
  runs between Loop start and Loop end, also in the worklet.
- Parameters declares the instrument's own parameters with a
  default. Sound FX sends the sound through a sound FX asset, its
  parameters as inputs, the sound set in where its Input was.
- compileInstrument walks the graph once per note. A trigger is on
  only for the notes it stands for, a silent source silences what it
  alone feeds, a Mix with a silent side is the other side. velocity
  and the parameters stay open for the voice. Builds are cached per
  note until the graph or a sound or FX it names changes.
- The player takes a note as one voice of several layers, each way
  with its own file and volume. release fades the gated ways out,
  one-shots play on. playNote can release after a duration.
- Play note plays one note with velocity, volume, duration and
  detached, and hands out voice for Set sound FX parameters and
  Stop sound. Velocity is always loudness. Instrument parameters
  picks values for the instrument's parameters like Sound FX
  parameters does for an FX, renames follow.
- The tab has the graph, a header field per parameter, Stop, and
  128 keys below. Keys without sound are grey. A key plays while it
  is held. Focused, the computer keyboard plays as in a tracker by
  KeyboardEvent.code, the arrows move the octave.

Findings:
- A label of the keys set fill on the shared small text style and
  darkened every small label of the editor. Caught in a screenshot
  before the commit, the keys have a style of their own now.
- Suite task 523 on cf6799a failed two checks of e2e 34 that timed
  audio by the page's clock: a 2.95 s echo tail was gone after 1 s,
  and Quad in was further along than 0.7 s allow. Both time on the
  audio clock now through a new hook __gm.sound.clock().

Tests:
- instrument.test.ts (new, 22): notes, asset, palette, round trip,
  compile per note, drum kit, zones, Mix, velocity and parameters,
  Sound FX node with rename, problems, cache, Play note, the keys
- sound-library +7 (layers, release, duration, early release, loop
  region in buffer and worklet), pitch-player +2 (loop region),
  node-catalog +4, graph adjusted. 582 tests in the touched files.
- e2e 4 and 34 on melektaus-atx: ALL PASSED, 34 with 44 checks (+7)
- Gate on melektaus-atx: CHECK EXIT 0, 243 test files, 3750 tests
- Counter-checks: any always on, release ending one-shots, Sound FX
  inputs ignored, loop region ignored. 3, 2, 1 and 1 tests failed.
- Browser probe on stein2: keys, held key, Single notes names and
  the header looked at in screenshots.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/runtime/systems/Audio.ts

@@ -1,5 +1,5 @@
 import type { EaseShare } from '../../core/model/animation';
-import type { FxParams, FxVoice } from '../../core/soundfx/nodes';
+import type { FxParams, FxPlan, FxVoice } from '../../core/soundfx/nodes';
 
 /**
  * What the runtime needs of the outside world to make a noise – the counterpart of `Input` on the
@@ -19,6 +19,25 @@ export interface AudioSink {
    * Returns the number of the voice, never used twice, or 0 where nothing is going to play.
    */
   play(file: string, volume: number, loop: boolean, owner: string, fx?: FxVoice): number;
+  /**
+   * Starts one note of an instrument (#331), as `play` starts a sound: `layers` are what the note is
+   * made of, played side by side as one voice, each way reading the file of its own source. `name`
+   * stands for the instrument. `params` fill in the parameters of the plans, its velocity among them.
+   * A `duration` above 0 releases it that many seconds after it starts; 0 holds it.
+   */
+  playNote(
+    name: string,
+    layers: readonly FxPlan[],
+    params: FxParams,
+    volume: number,
+    owner: string,
+    duration: number,
+  ): number;
+  /**
+   * The end of a note (#331): its ways that end with the note fade out, those that play through
+   * go on. Nothing happens for a voice that is no note or not there.
+   */
+  release(voice: number): void;
   /**
    * Hands new values to the sound FX parameters of one voice, by the number `play` gave it (#315).
    * A name its FX does not have is left out, one not given keeps its value. A voice that has ended
@@ -51,6 +70,8 @@ export interface AudioSink {
 
 export const SILENT_AUDIO: AudioSink = {
   play: () => 0,
+  playNote: () => 0,
+  release: () => {},
   tune: () => {},
   length: () => 0,
   tail: () => 0,

src/runtime/systems/behaviorContext.ts

@@ -16,6 +16,9 @@ import { hasRenderLayer } from '../../core/properties/PropertySchema';
 import { resolveAssetProps } from '../../core/properties/resolve';
 import { loopsOf, volumeOf } from '../../core/properties/sounds';
 import { soundFxBuildFor } from '../../core/soundfx/compile';
+import { instrumentBuildFor, instrumentSourcesOf } from '../../core/instrument/compile';
+import { VELOCITY_PARAM } from '../../core/instrument/nodes';
+import { heldNote } from '../../core/instrument/notes';
 import { DRY_VOICE, type FxParams } from '../../core/soundfx/nodes';
 import type { Entity } from '../Entity';
 import { PhysicsSystem } from '../physics/PhysicsSystem';
@@ -166,6 +169,8 @@ export function behaviorContext(
     },
     playSound: (assetId, volume, loop, detached, fx, fxParams) =>
       playSound(run, assetId, volume, loop, detached ? '' : entity.id, fx, fxParams),
+    playNote: (instrumentId, note, velocity, volume, duration, detached, params) =>
+      playNote(run, instrumentId, { note, velocity, volume, duration }, detached ? '' : entity.id, params),
     soundLength: (assetId) => {
       const file = soundFileOf(project, assetId);
       return file ? run.audio.length(file) : 0;
@@ -251,6 +256,34 @@ function playSound(
   );
 }
 
+/**
+ * One note of an instrument (#331), as the sink understands it: the layers the instrument makes of
+ * it, the velocity as loudness and as the value of its `velocity`, and the voice's volume held to
+ * 0..1 like a sound's. An instrument that plays nothing for that note plays nothing at all.
+ */
+export function playNote(
+  { project, audio }: Pick<ContextSources, 'project' | 'audio'>,
+  instrumentId: string,
+  struck: { note: number; velocity: number; volume: number; duration: number },
+  owner: string,
+  params: FxParams,
+): number {
+  const asset = findAssetOf(project, instrumentId, 'instrument');
+  if (!asset) return 0;
+  const { layers } = instrumentBuildFor(asset, heldNote(struck.note), instrumentSourcesOf(project));
+  if (layers.length === 0) return 0;
+  const velocity = Number.isFinite(struck.velocity) ? Math.max(0, Math.min(1, struck.velocity)) : 1;
+  const level = Math.max(0, Math.min(1, struck.volume * velocity));
+  const duration = Number.isFinite(struck.duration) ? Math.max(0, struck.duration) : 0;
+  const values = { ...params, [VELOCITY_PARAM]: velocity };
+  return audio.playNote(instrumentVoiceName(instrumentId), layers, values, level, owner, duration);
+}
+
+/** What a note's voice is named by, where a sound's is named by its file. */
+export function instrumentVoiceName(instrumentId: string): string {
+  return `instrument:${instrumentId}`;
+}
+
 /** Where a ray of that length ends; where it has no direction, where it starts. */
 function pointAlong(from: Vec2, direction: Vec2, length: number): Vec2 {
   const d = Math.hypot(direction.x, direction.y);