Make an 8-bit sound with a Preset, Randomize or Mutate (#329)

A Chip could play a sound, but finding a good one meant typing a dozen
numbers. sfxr's buttons do that in one click: a kind of sound drawn
anew every time, a wild draw, or a small nudge. The Instrument tab now
has the same, and plays the result at once.

- Preset menu with Pickup, Laser, Explosion, Powerup, Hit, Jump and
  Blip. It puts a new graph in place of the instrument's, as one undo
  step: Notes for all 128 notes, Chip, Envelope, Filter, Bitcrusher,
  Output. The Chip keeps its own frequency with follow note off, so
  every key plays the same effect, and sustain 0 ends it by itself.
- The presets are sfxr's generators, worked out into Hz, semitones and
  seconds with sfxr's own formulas, in chipPresets.ts. sfxr's envelope
  holds and falls in a line, ours falls quick at first. So the decay
  is three times sfxr's hold and fall.
- Randomize draws every number of the Chips, Envelopes, Filters and
  Bitcrushers anew, as sfxr's randomizer does. Waves, filter types,
  the Bitcrusher's mix and an Envelope's from and to stay.
- Mutate moves each of those numbers a little, one in two. A 0 stays
  0, so nothing that was off comes on.
- An input fed by an edge is left alone by both. Both are grey while
  the graph has none of those nodes.
- Audition, off by default as in the Pattern tab, plays the note last
  played again 150 ms after a change to the graph rests.
- Preset, Randomize and Mutate always play that note, for up to 2 s.
- ReplaceGraphCommand swaps nodes and edges and keeps groups and notes.
- The info on the right of the header kept 220 px and was cut off
  with the four new buttons. 140 px still fit "No sound picked".

Not done: punch, filter sweeps and the phaser of sfxr (#341).

Tests:
- Unit chip-presets (new) 7. Counter-check: a wrong Hz formula and
  fed inputs not left alone turn 3 of them red. Unit tests of the
  instrument tab, graph commands and sound FX nodes: 49 files, 851
  green.
- e2e 34 (melektaus-atx): ALL PASSED, 64 checks (4 new): Preset,
  Randomize and Mutate, Audition, three undos back to the Sample.
- Screenshot with a Laser preset: the header fits at 1280 px, the
  chain is fitted, the Chip is a saw with its duty grey.
- Gate (melektaus-atx): CHECK EXIT 0, 256 files, 3969 tests.

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

src/core/commands/graphCommands.ts

@@ -326,6 +326,31 @@ function setCollapsed(node: GraphNode, collapsed: boolean): void {
   else delete node.collapsed;
 }
 
+/** Other nodes and edges in place of a graph's, as one step: an instrument's Preset (#329). Groups and notes stay. */
+export class ReplaceGraphCommand implements Command {
+  private previous?: Pick<Graph, 'nodes' | 'edges'>;
+
+  constructor(
+    private readonly assetId: string,
+    private readonly graph: Pick<Graph, 'nodes' | 'edges'>,
+    readonly label: string,
+  ) {}
+
+  execute(project: Project): void {
+    const graph = requireGraph(project, this.assetId);
+    this.previous = { nodes: graph.nodes, edges: graph.edges };
+    graph.nodes = structuredClone(this.graph.nodes);
+    graph.edges = structuredClone(this.graph.edges);
+  }
+
+  undo(project: Project): void {
+    if (!this.previous) return;
+    const graph = requireGraph(project, this.assetId);
+    graph.nodes = this.previous.nodes;
+    graph.edges = this.previous.edges;
+  }
+}
+
 export class DisconnectCommand implements Command {
   readonly label = 'Disconnect';
   private removed: Removed<GraphEdge>[] = [];

src/core/instrument/chipPresets.ts

@@ -0,0 +1,457 @@
+import { edgesInto, type Graph, type GraphEdge, type GraphNode } from '../graph/Graph';
+import { asNumber } from '../graph/values';
+import { newId } from '../ids';
+import type { PropertyBag } from '../model/Properties';
+import type { FlatDef } from '../properties/PropertySchema';
+import type { ChipWave } from '../soundfx/chip';
+import {
+  CRUSH_ROWS,
+  FILTER_ROWS,
+  type FxPassFilter,
+  passOf,
+  SoundFxBitcrusher,
+  SoundFxFilter,
+} from '../soundfx/nodes';
+import {
+  CHIP_ROWS,
+  ENVELOPE_ROWS,
+  INSTRUMENT_CHIP,
+  INSTRUMENT_ENVELOPE,
+  INSTRUMENT_NOTES,
+  INSTRUMENT_OUTPUT,
+} from './nodes';
+import { HIGHEST_NOTE, LOWEST_NOTE } from './notes';
+
+/**
+ * The Preset menu, Randomize and Mutate of the Instrument tab (#329), the way sfxr makes its sounds:
+ * its generators and its randomizer draw sfxr's settings, 0 to 1 as its sliders have them, which are
+ * then worked out into the numbers of a Chip, an Envelope, a Filter and a Bitcrusher. sfxr is
+ * Copyright (c) 2007 Tomas Pettersson, MIT licence.
+ */
+export type ChipPreset = 'pickup' | 'laser' | 'explosion' | 'powerup' | 'hit' | 'jump' | 'blip';
+
+export const CHIP_PRESETS: readonly { value: ChipPreset; label: string }[] = [
+  { value: 'pickup', label: 'Pickup' },
+  { value: 'laser', label: 'Laser' },
+  { value: 'explosion', label: 'Explosion' },
+  { value: 'powerup', label: 'Powerup' },
+  { value: 'hit', label: 'Hit' },
+  { value: 'jump', label: 'Jump' },
+  { value: 'blip', label: 'Blip' },
+];
+
+type Random = () => number;
+
+/** sfxr's settings by its own names, with the wave as ours. */
+interface Sfxr {
+  wave: ChipWave;
+  baseFreq: number;
+  freqLimit: number;
+  freqRamp: number;
+  freqDramp: number;
+  duty: number;
+  dutyRamp: number;
+  vibStrength: number;
+  vibSpeed: number;
+  envAttack: number;
+  envSustain: number;
+  envDecay: number;
+  lpfFreq: number;
+  lpfResonance: number;
+  hpfFreq: number;
+  repeatSpeed: number;
+  arpSpeed: number;
+  arpMod: number;
+}
+
+const reset = (): Sfxr => ({
+  wave: 'square',
+  baseFreq: 0.3,
+  freqLimit: 0,
+  freqRamp: 0,
+  freqDramp: 0,
+  duty: 0,
+  dutyRamp: 0,
+  vibStrength: 0,
+  vibSpeed: 0,
+  envAttack: 0,
+  envSustain: 0.3,
+  envDecay: 0.4,
+  lpfFreq: 1,
+  lpfResonance: 0,
+  hpfFreq: 0,
+  repeatSpeed: 0,
+  arpSpeed: 0,
+  arpMod: 0,
+});
+
+/** sfxr's waves by their number there. */
+const SFXR_WAVES: readonly ChipWave[] = ['square', 'saw', 'sine', 'noise'];
+
+/** sfxr's generators, one per button. */
+function presetSfxr(preset: ChipPreset, random: Random): Sfxr {
+  const p = reset();
+  // sfxr's `frnd`: 0 up to `range`, and `rnd`: a whole number from 0 to `n`, both included.
+  const f = (range: number) => random() * range;
+  const r = (n: number) => Math.floor(random() * (n + 1));
+  switch (preset) {
+    case 'pickup':
+      p.baseFreq = 0.4 + f(0.5);
+      p.envSustain = f(0.1);
+      p.envDecay = 0.1 + f(0.4);
+      if (r(1)) {
+        p.arpSpeed = 0.5 + f(0.2);
+        p.arpMod = 0.2 + f(0.4);
+      }
+      break;
+    case 'laser': {
+      let wave = r(2);
+      if (wave === 2 && r(1)) wave = r(1);
+      p.wave = SFXR_WAVES[wave]!;
+      p.baseFreq = 0.5 + f(0.5);
+      p.freqLimit = Math.max(0.2, p.baseFreq - 0.2 - f(0.6));
+      p.freqRamp = -0.15 - f(0.2);
+      if (r(2) === 0) {
+        p.baseFreq = 0.3 + f(0.6);
+        p.freqLimit = f(0.1);
+        p.freqRamp = -0.35 - f(0.3);
+      }
+      if (r(1)) {
+        p.duty = f(0.5);
+        p.dutyRamp = f(0.2);
+      } else {
+        p.duty = 0.4 + f(0.5);
+        p.dutyRamp = -f(0.7);
+      }
+      p.envSustain = 0.1 + f(0.2);
+      p.envDecay = f(0.4);
+      if (r(1)) p.hpfFreq = f(0.3);
+      break;
+    }
+    case 'explosion':
+      p.wave = 'noise';
+      if (r(1)) {
+        p.baseFreq = 0.1 + f(0.4);
+        p.freqRamp = -0.1 + f(0.4);
+      } else {
+        p.baseFreq = 0.2 + f(0.7);
+        p.freqRamp = -0.2 - f(0.2);
+      }
+      p.baseFreq *= p.baseFreq;
+      if (r(4) === 0) p.freqRamp = 0;
+      if (r(2) === 0) p.repeatSpeed = 0.3 + f(0.5);
+      p.envSustain = 0.1 + f(0.3);
+      p.envDecay = f(0.5);
+      if (r(1)) {
+        p.vibStrength = f(0.7);
+        p.vibSpeed = f(0.6);
+      }
+      if (r(2) === 0) {
+        p.arpSpeed = 0.6 + f(0.3);
+        p.arpMod = 0.8 - f(1.6);
+      }
+      break;
+    case 'powerup':
+      if (r(1)) p.wave = 'saw';
+      else p.duty = f(0.6);
+      p.baseFreq = 0.2 + f(0.3);
+      if (r(1)) {
+        p.freqRamp = 0.1 + f(0.4);
+        p.repeatSpeed = 0.4 + f(0.4);
+      } else {
+        p.freqRamp = 0.05 + f(0.2);
+        if (r(1)) {
+          p.vibStrength = f(0.7);
+          p.vibSpeed = f(0.6);
+        }
+      }
+      p.envSustain = f(0.4);
+      p.envDecay = 0.1 + f(0.4);
+      break;
+    case 'hit': {
+      const wave = r(2);
+      p.wave = SFXR_WAVES[wave === 2 ? 3 : wave]!;
+      if (p.wave === 'square') p.duty = f(0.6);
+      p.baseFreq = 0.2 + f(0.6);
+      p.freqRamp = -0.3 - f(0.4);
+      p.envSustain = f(0.1);
+      p.envDecay = 0.1 + f(0.2);
+      if (r(1)) p.hpfFreq = f(0.3);
+      break;
+    }
+    case 'jump':
+      p.duty = f(0.6);
+      p.baseFreq = 0.3 + f(0.3);
+      p.freqRamp = 0.1 + f(0.2);
+      p.envSustain = 0.1 + f(0.3);
+      p.envDecay = 0.1 + f(0.2);
+      if (r(1)) p.hpfFreq = f(0.3);
+      if (r(1)) p.lpfFreq = 1 - f(0.6);
+      break;
+    case 'blip':
+      p.wave = SFXR_WAVES[r(1)]!;
+      if (p.wave === 'square') p.duty = f(0.6);
+      p.baseFreq = 0.2 + f(0.4);
+      p.envSustain = 0.1 + f(0.1);
+      p.envDecay = f(0.2);
+      p.hpfFreq = 0.1;
+      break;
+  }
+  return p;
+}
+
+/** sfxr's Randomize: every setting drawn, most of them leaning towards 0. */
+function randomSfxr(random: Random): Sfxr {
+  const signed = () => random() * 2 - 1;
+  const p = reset();
+  p.baseFreq = signed() ** 2;
+  if (random() < 0.5) p.baseFreq = signed() ** 3 + 0.5;
+  p.freqRamp = signed() ** 5;
+  if (p.baseFreq > 0.7 && p.freqRamp > 0.2) p.freqRamp = -p.freqRamp;
+  if (p.baseFreq < 0.2 && p.freqRamp < -0.05) p.freqRamp = -p.freqRamp;
+  p.freqDramp = signed() ** 3;
+  p.duty = signed();
+  p.dutyRamp = signed() ** 3;
+  p.vibStrength = signed() ** 3;
+  p.vibSpeed = signed();
+  p.envAttack = signed() ** 3;
+  p.envSustain = signed() ** 2;
+  p.envDecay = signed();
+  if (p.envAttack + p.envSustain + p.envDecay < 0.2) {
+    p.envSustain += 0.2 + random() * 0.3;
+    p.envDecay += 0.2 + random() * 0.3;
+  }
+  p.lpfResonance = signed();
+  p.lpfFreq = 1 - random() ** 3;
+  p.hpfFreq = random() ** 5;
+  p.repeatSpeed = signed();
+  p.arpSpeed = signed();
+  p.arpMod = signed();
+  return p;
+}
+
+const SFXR_RATE = 44100;
+/** sfxr counts a period in samples taken 8 times over: its frequency is `f² + 0.001` of 3528 Hz. */
+const hzOf = (f: number) => 3528 * (f * f + 0.001);
+/** How long sfxr waits before an arpeggio or a repeat, at a speed from 0 to 1. */
+const waitOf = (speed: number) => ((1 - speed) ** 2 * 20000 + 32) / SFXR_RATE;
+/** A stage of sfxr's envelope: its setting squared, in 100000 samples. */
+const stageOf = (value: number) => (value * value * 100000) / SFXR_RATE;
+
+function chipNumbers(p: Sfxr): Record<keyof typeof CHIP_ROWS, number> {
+  const slide = 1 - p.freqRamp ** 3 * 0.01;
+  const arpeggio = p.arpMod >= 0 ? 1 - p.arpMod ** 2 * 0.9 : 1 + p.arpMod ** 2 * 10;
+  return {
+    frequency: hzOf(p.baseFreq),
+    duty: 0.5 - p.duty * 0.5,
+    dutySweep: -p.dutyRamp * 0.00005 * SFXR_RATE,
+    slide: -12 * Math.log2(slide) * SFXR_RATE,
+    deltaSlide: (12 / Math.LN2) * SFXR_RATE ** 2 * p.freqDramp ** 3 * 1e-6,
+    minFrequency: p.freqLimit > 0 ? hzOf(p.freqLimit) : 0,
+    vibratoDepth: 12 * Math.log2(1 + Math.abs(p.vibStrength) * 0.5),
+    vibratoSpeed: (p.vibSpeed ** 2 * 0.01 * SFXR_RATE) / (2 * Math.PI),
+    arpeggio: p.arpSpeed === 1 || p.arpMod === 0 ? 0 : -12 * Math.log2(arpeggio),
+    arpeggioTime: waitOf(p.arpSpeed),
+    repeat: p.repeatSpeed === 0 ? 0 : waitOf(p.repeatSpeed),
+  };
+}
+
+/**
+ * sfxr holds a sound at full for its sustain, then lets it fall in a straight line; an Envelope
+ * falls away as a struck string does, quick at first. Three times the whole of sfxr's keeps about
+ * as much of it heard. Sustain 0 ends the note once it has fallen.
+ */
+const FALL = 3;
+const RELEASE = 0.02;
+
+function envelopeNumbers(p: Sfxr): Record<'attack' | 'decay' | 'sustain' | 'release', number> {
+  return {
+    attack: stageOf(p.envAttack),
+    decay: FALL * (stageOf(p.envSustain) + stageOf(p.envDecay)),
+    sustain: 0,
+    release: RELEASE,
+  };
+}
+
+/** Where sfxr's filters come out, run 8 times a sample: about 17.8 kHz times `f^1.5` low, 5.6 kHz times `f²` high. */
+function filterNumbers(p: Sfxr, filter: FxPassFilter): Record<'cutoff' | 'resonance', number> {
+  if (filter === 'highpass') return { cutoff: 5615 * p.hpfFreq ** 2, resonance: 0 };
+  // Wide open, as far as the row goes.
+  if (p.lpfFreq >= 1) return { cutoff: Infinity, resonance: 0 };
+  return { cutoff: 17756 * Math.max(0, p.lpfFreq) ** 1.5, resonance: Math.abs(p.lpfResonance) };
+}
+
+/** A number held to its row and rounded to as many places as its step has. */
+function heldTo(value: number, row: FlatDef<'number'>): number {
+  const places = Math.max(0, -Math.floor(Math.log10(row.step ?? 0.01)));
+  const inside = Math.max(row.min ?? -Infinity, Math.min(row.max ?? Infinity, value));
+  return Number(inside.toFixed(places)) + 0;
+}
+
+function held<K extends string>(
+  values: Record<K, number>,
+  rows: Record<NoInfer<K>, FlatDef<'number'>>,
+): Record<K, number> {
+  const out = {} as Record<K, number>;
+  for (const key of Object.keys(values) as K[]) out[key] = heldTo(values[key], rows[key]);
+  return out;
+}
+
+/** Room between the nodes of a preset, left to right. */
+const COLUMN = 240;
+
+/**
+ * A preset as a whole graph (#329): every note plays one Chip, which ends by itself through an
+ * Envelope, a Filter and a Bitcrusher. The Chip keeps to the preset's own frequency, as sfxr does,
+ * so every key plays the same sound until "follow note" is turned on. Each call draws it anew.
+ */
+export function chipPresetGraph(preset: ChipPreset, random: Random = Math.random): Graph {
+  const p = presetSfxr(preset, random);
+  const filter: FxPassFilter = p.lpfFreq >= 1 && p.hpfFreq > 0 ? 'highpass' : 'lowpass';
+  const crushed = random() < 0.5;
+  const node = (type: string, column: number, params: PropertyBag): GraphNode => ({
+    id: newId(),
+    type,
+    x: column * COLUMN,
+    y: 0,
+    params,
+  });
+  const notes = node(INSTRUMENT_NOTES, 0, { from: String(LOWEST_NOTE), to: String(HIGHEST_NOTE) });
+  const chip = node(INSTRUMENT_CHIP, 1, {
+    wave: p.wave,
+    followNote: false,
+    ...held(chipNumbers(p), CHIP_ROWS),
+  });
+  const envelope = node(INSTRUMENT_ENVELOPE, 2, held(envelopeNumbers(p), ENVELOPE_ROWS));
+  const pass = node(SoundFxFilter.type, 3, { filter, ...held(filterNumbers(p, filter), FILTER_ROWS) });
+  const crush = node(
+    SoundFxBitcrusher.type,
+    4,
+    held({ bits: crushed ? 8 : 16, rate: crushed ? 22050 : 44100, mix: 1 }, CRUSH_ROWS),
+  );
+  const output = node(INSTRUMENT_OUTPUT, 5, {});
+  const wire = (from: GraphNode, out: string, to: GraphNode, into: string): GraphEdge => ({
+    id: newId(),
+    from: { node: from.id, port: out },
+    to: { node: to.id, port: into },
+  });
+  return {
+    nodes: [notes, chip, envelope, pass, crush, output],
+    edges: [
+      wire(notes, 'any', chip, 'trigger'),
+      wire(chip, 'out', envelope, 'in'),
+      wire(envelope, 'out', pass, 'in'),
+      wire(pass, 'out', crush, 'in'),
+      wire(crush, 'out', output, 'in'),
+    ],
+  };
+}
+
+/** One number Randomize or Mutate gives a node. */
+export interface ParamChange {
+  node: string;
+  key: string;
+  value: number;
+}
+
+function rowsOf(type: string): Record<string, FlatDef<'number'>> | null {
+  switch (type) {
+    case INSTRUMENT_CHIP:
+      return CHIP_ROWS;
+    case INSTRUMENT_ENVELOPE:
+      return ENVELOPE_ROWS;
+    case SoundFxFilter.type:
+      return FILTER_ROWS;
+    case SoundFxBitcrusher.type:
+      return CRUSH_ROWS;
+    default:
+      return null;
+  }
+}
+
+/** Whether Randomize and Mutate find anything in a graph to change. */
+export const hasChipNumbers = (graph: Graph): boolean =>
+  graph.nodes.some((node) => rowsOf(node.type) !== null);
+
+/** An input an edge feeds keeps what it is fed: a number typed in there would do nothing. */
+const typedIn = (graph: Graph, node: GraphNode) => (key: string) =>
+  edgesInto(graph, node.id, key).length === 0;
+
+function randomNumbers(node: GraphNode, random: Random): Record<string, number> | null {
+  switch (node.type) {
+    case INSTRUMENT_CHIP:
+      return held(chipNumbers(randomSfxr(random)), CHIP_ROWS);
+    case INSTRUMENT_ENVELOPE:
+      return held(envelopeNumbers(randomSfxr(random)), ENVELOPE_ROWS);
+    case SoundFxFilter.type:
+      return held(filterNumbers(randomSfxr(random), passOf(node.params)), FILTER_ROWS);
+    case SoundFxBitcrusher.type:
+      return held({ bits: 4 + random() * 12, rate: 2000 * 24 ** random() }, CRUSH_ROWS);
+    default:
+      return null;
+  }
+}
+
+/**
+ * Randomize (#329): the numbers of every Chip, Envelope, Filter and Bitcrusher drawn anew, as sfxr's
+ * randomizer draws them. Waves, filter types, the Mix of a Bitcrusher and an Envelope's "from" and
+ * "to" stay, and so does everything else in the graph.
+ */
+export function randomizedParams(graph: Graph, random: Random = Math.random): ParamChange[] {
+  const changes: ParamChange[] = [];
+  for (const node of graph.nodes) {
+    const values = randomNumbers(node, random);
+    if (!values) continue;
+    const open = typedIn(graph, node);
+    for (const [key, value] of Object.entries(values))
+      if (open(key)) changes.push({ node: node.id, key, value });
+  }
+  return changes;
+}
+
+/** How far Mutate moves a number at most: a share of an octave where it is heard as a ratio, else a step and a tenth of it. */
+const MUTATE: Readonly<Record<string, { octaves: number } | { by: number }>> = {
+  frequency: { octaves: 0.25 },
+  minFrequency: { octaves: 0.25 },
+  cutoff: { octaves: 0.25 },
+  rate: { octaves: 0.25 },
+  duty: { by: 0.025 },
+  dutySweep: { by: 0.1 },
+  slide: { by: 5 },
+  deltaSlide: { by: 20 },
+  vibratoDepth: { by: 0.2 },
+  vibratoSpeed: { by: 0.5 },
+  arpeggio: { by: 1 },
+  arpeggioTime: { by: 0.01 },
+  repeat: { by: 0.02 },
+  attack: { by: 0.005 },
+  decay: { by: 0.02 },
+  release: { by: 0.01 },
+  resonance: { by: 0.05 },
+  bits: { by: 0.5 },
+};
+
+/**
+ * Mutate (#329): as sfxr does, each number of those nodes moves a little or not at all, one in two.
+ * A 0 stays 0, so nothing that was off comes on, and an Envelope keeps its sustain.
+ */
+export function mutatedParams(graph: Graph, random: Random = Math.random): ParamChange[] {
+  const changes: ParamChange[] = [];
+  for (const node of graph.nodes) {
+    const rows = rowsOf(node.type);
+    if (!rows) continue;
+    const open = typedIn(graph, node);
+    for (const row of Object.values(rows)) {
+      const how = MUTATE[row.key];
+      if (!how || !open(row.key) || random() < 0.5) continue;
+      const now = asNumber(node.params[row.key] ?? row.default);
+      if (now === 0) continue;
+      const u = random() * 2 - 1;
+      const moved =
+        'octaves' in how ? now * 2 ** (u * how.octaves) : now + u * (how.by + Math.abs(now) * 0.1);
+      const value = heldTo(moved, row);
+      if (value !== now) changes.push({ node: node.id, key: row.key, value });
+    }
+  }
+  return changes;
+}

src/core/soundfx/nodes.ts

@@ -389,6 +389,7 @@ export function passQ(filter: FxPassFilter, resonance: number): number {
 
 const CUTOFF = { ...numberRow('cutoff', 'Cutoff (Hz)', 20, 20000, 1), default: 1000 };
 const RESONANCE = numberRow('resonance', 'Resonance', 0, 1, 0.01);
+export const FILTER_ROWS = { cutoff: CUTOFF, resonance: RESONANCE };
 const PASS_FILTERS: { value: FxPassFilter; label: string }[] = [
   { value: 'lowpass', label: 'Low-pass' },
   { value: 'highpass', label: 'High-pass' },
@@ -402,7 +403,7 @@ const PASS = {
   options: PASS_FILTERS,
 };
 
-function passOf(settings: PropertyBag): FxPassFilter {
+export function passOf(settings: PropertyBag): FxPassFilter {
   return PASS_FILTERS.find((option) => option.value === settings[PASS.key])?.value ?? 'lowpass';
 }
 
@@ -512,6 +513,7 @@ export const SoundFxDelay: SoundFxNodeDef = {
 const CRUSH_BITS = { ...numberRow('bits', 'Bits', 1, 16, 0.1), default: 8 };
 const CRUSH_RATE = { ...numberRow('rate', 'Rate (Hz)', 100, 48000, 1), default: 8000 };
 const CRUSH_MIX = { ...numberRow('mix', 'Mix', 0, 1, 0.01), default: 1 };
+export const CRUSH_ROWS = { bits: CRUSH_BITS, rate: CRUSH_RATE, mix: CRUSH_MIX };
 
 export const SoundFxBitcrusher: SoundFxNodeDef = {
   type: 'SoundFxBitcrusher',

src/editor/debug/graphHooks.ts

@@ -135,6 +135,13 @@ export function graphHooks({ state, editor }: HookContext) {
       }),
       keyAt: (note: number) => editor.instrumentEditor.keyboard.keyCentre(note),
       stopAt: () => centreOf(editor.instrumentEditor.stopButton),
+      presetAt: () => centreOf(editor.instrumentEditor.presetButton),
+      randomizeAt: () => centreOf(editor.instrumentEditor.randomizeButton),
+      mutateAt: () => centreOf(editor.instrumentEditor.mutateButton),
+      auditionAt: () => ({
+        ...centreOf(editor.instrumentEditor.auditionButton),
+        toggled: editor.instrumentEditor.auditionButton.toggled,
+      }),
       params: () => editor.instrumentEditor.previewValues,
       setParam: (key: string, value: number) => editor.instrumentEditor.setPreviewValue(key, value),
     },

src/editor/instrument/InstrumentEditor.ts

@@ -1,3 +1,14 @@
+import { CompoundCommand } from '../../core/commands/CompoundCommand';
+import { ReplaceGraphCommand, SetNodeParamCommand } from '../../core/commands/graphCommands';
+import {
+  CHIP_PRESETS,
+  type ChipPreset,
+  chipPresetGraph,
+  hasChipNumbers,
+  mutatedParams,
+  type ParamChange,
+  randomizedParams,
+} from '../../core/instrument/chipPresets';
 import {
   instrumentBuildFor,
   instrumentCheck,
@@ -5,10 +16,21 @@ import {
   instrumentSourcesOf,
   playedNotes,
 } from '../../core/instrument/compile';
-import { noteName } from '../../core/instrument/notes';
+import { MIDDLE_C, noteName } from '../../core/instrument/notes';
 import type { Asset, InstrumentAsset } from '../../core/model/Asset';
 import { playNote } from '../../runtime/systems/behaviorContext';
-import { Button, HStack, Label, NumberField, Stack, Theme, VStack, type Widget } from '../../ui';
+import {
+  Button,
+  Dropdown,
+  HStack,
+  Label,
+  Menu,
+  NumberField,
+  Stack,
+  Theme,
+  VStack,
+  type Widget,
+} from '../../ui';
 import { soundLibrary } from '../../viewport/SoundLibrary';
 import { AssetTabEditor } from '../AssetTabEditor';
 import { GraphCanvas } from '../graph/GraphCanvas';
@@ -17,22 +39,34 @@ import { TOOLBAR_ICON_SVG } from '../panels/toolbarIcons';
 import type { EditorState } from '../state';
 import { PianoKeyboard } from './PianoKeyboard';
 
-/** Room kept for "N notes", or for the reason the graph does not compile. */
-const INFO_WIDTH = 220;
+/** Room kept for "N notes", or for the reason the graph does not compile: "No sound picked" fits, a longer one is cut. */
+const INFO_WIDTH = 140;
 const PARAM_WIDTH = 48;
 /** Whose voices the tab's Stop silences: its own, never a running game's. */
 const PREVIEW_OWNER = 'instrument-preview';
+/** How long a note is heard after a Preset, Randomize, Mutate or a change with Audition on: a held one is let go then. */
+const AUDITION_SECONDS = 2;
+/** How long a change waits to be heard with Audition on, so dragging a number plays once it rests. */
+const AUDITION_DELAY_MS = 150;
 
 /**
  * The nodes of one instrument (#331), and below them its keys: a note is heard while a key is held,
  * by the pointer or by the computer keyboard. The header holds a value for each of its parameters –
- * the tab's own, never written into the asset – and a Stop for everything the tab still plays.
+ * the tab's own, never written into the asset – and a Stop for everything the tab still plays. Its
+ * Preset menu, Randomize and Mutate make 8-bit sounds the way sfxr does (#329) and play them at once.
  */
 export class InstrumentEditor extends AssetTabEditor<InstrumentAsset, GraphCanvas> {
   readonly snap = new SnapToggle(() => this.canvas);
   /** Public for the check scripts. */
   readonly keyboard = new PianoKeyboard();
   readonly stopButton: Button;
+  readonly presetButton: Dropdown;
+  readonly randomizeButton: Button;
+  readonly mutateButton: Button;
+  /** Whether a change to the graph is heard; off by default, as in the Pattern tab. */
+  readonly auditionButton: Button;
+  /** The note a Preset, Randomize, Mutate or Audition plays: the one last played. */
+  lastNote = MIDDLE_C;
   private readonly octaveLabel = new Label('', { style: 'small' });
   private readonly paramBar = new HStack({ gap: Theme.gap, align: 'center' });
   private readonly paramFields = new Map<string, NumberField>();
@@ -42,10 +76,31 @@ export class InstrumentEditor extends AssetTabEditor<InstrumentAsset, GraphCanva
   private valuesFor = '';
   /** The voices the tab started that may still be playing – what a moved field reaches. */
   private voices: number[] = [];
+  /** The graph as last heard or shown, by `soundPrint`, and whose it was. */
+  private heard = '';
+  private heardFor = '';
+  private auditionTimer: ReturnType<typeof setTimeout> | undefined;
 
   constructor(state: EditorState) {
     super(state, { infoWidth: INFO_WIDTH });
     this.stopButton = new Button('Stop', { icon: TOOLBAR_ICON_SVG.stop, onClick: () => this.stop() });
+    this.presetButton = new Dropdown('Preset', {
+      tooltip: 'Make the instrument an 8-bit sound of that kind, drawn anew every time',
+      onClick: () => this.openPresetMenu(),
+    });
+    this.randomizeButton = new Button('Randomize', {
+      tooltip: 'Draw every number of the Chips, Envelopes, Filters and Bitcrushers anew',
+      onClick: () => this.randomize(),
+    });
+    this.mutateButton = new Button('Mutate', {
+      tooltip: 'Move some numbers of the Chips, Envelopes, Filters and Bitcrushers a little',
+      onClick: () => this.mutate(),
+    });
+    this.auditionButton = new Button('Audition', {
+      toggle: true,
+      tooltip: 'Play the last note again when the instrument changes',
+      onClick: () => this.auditionButton.setToggled(!this.auditionButton.toggled),
+    });
     this.keyboard.onNoteOn = (note) => this.playNote(note);
     this.keyboard.onNoteOff = (voice) => soundLibrary.release(voice);
     this.keyboard.isPlaying = (voice) => soundLibrary.playing(voice);
@@ -54,12 +109,17 @@ export class InstrumentEditor extends AssetTabEditor<InstrumentAsset, GraphCanva
     this.mount(new GraphCanvas(state, 'instrument'), [
       ...this.snap.widgets,
       this.stopButton,
+      this.presetButton,
+      this.randomizeButton,
+      this.mutateButton,
+      this.auditionButton,
       this.octaveLabel,
       this.paramBar,
     ]);
     this.syncOctave();
     state.on('load', () => {
       this.valuesFor = '';
+      this.heardFor = '';
     });
   }
 
@@ -89,11 +149,12 @@ export class InstrumentEditor extends AssetTabEditor<InstrumentAsset, GraphCanva
     this.setValue(key, value);
   }
 
-  /** Starts one note as the keys do, held until it is released; gives back its voice. */
-  playNote(note: number): number {
+  /** Starts one note as the keys do, held until it is released or for `duration` seconds; gives back its voice. */
+  playNote(note: number, duration = 0): number {
     const asset = this.asset();
     if (!asset) return 0;
-    const struck = { note, velocity: 1, volume: 1, duration: 0 };
+    this.lastNote = note;
+    const struck = { note, velocity: 1, volume: 1, duration };
     const voice = playNote(
       { project: this.state.project, audio: soundLibrary },
       asset.id,
@@ -105,6 +166,47 @@ export class InstrumentEditor extends AssetTabEditor<InstrumentAsset, GraphCanva
     return voice;
   }
 
+  /** Plays the note last played on its own, for a while: what Preset, Randomize, Mutate and Audition do. */
+  audition(): number {
+    clearTimeout(this.auditionTimer);
+    this.stop();
+    return this.playNote(this.lastNote, AUDITION_SECONDS);
+  }
+
+  applyPreset(preset: ChipPreset): void {
+    const asset = this.asset();
+    if (!asset) return;
+    const label = CHIP_PRESETS.find((option) => option.value === preset)?.label ?? preset;
+    if (!this.state.execute(new ReplaceGraphCommand(asset.id, chipPresetGraph(preset), `Preset ${label}`)))
+      return;
+    this.canvas.fit();
+    this.audition();
+  }
+
+  randomize(): void {
+    const asset = this.asset();
+    if (asset) this.change('Randomize', randomizedParams(asset.graph));
+  }
+
+  mutate(): void {
+    const asset = this.asset();
+    if (asset) this.change('Mutate', mutatedParams(asset.graph));
+  }
+
+  private change(label: string, changes: readonly ParamChange[]): void {
+    const asset = this.asset();
+    if (!asset || changes.length === 0) return;
+    const commands = changes.map((c) => new SetNodeParamCommand(asset.id, c.node, c.key, c.value));
+    if (this.state.execute(new CompoundCommand(label, commands))) this.audition();
+  }
+
+  private openPresetMenu(): void {
+    if (!this.asset()) return;
+    new Menu(
+      CHIP_PRESETS.map((preset) => ({ label: preset.label, onSelect: () => this.applyPreset(preset.value) })),
+    ).openBelow(this.presetButton);
+  }
+
   stop(): void {
     this.keyboard.releaseAll();
     soundLibrary.stopOwner(PREVIEW_OWNER);
@@ -137,10 +239,26 @@ export class InstrumentEditor extends AssetTabEditor<InstrumentAsset, GraphCanva
   protected override syncExtras(asset: InstrumentAsset | null): void {
     this.snap.setEnabled(Boolean(asset));
     this.stopButton.setEnabled(Boolean(asset));
+    this.presetButton.setEnabled(Boolean(asset));
+    this.randomizeButton.setEnabled(Boolean(asset && hasChipNumbers(asset.graph)));
+    this.mutateButton.setEnabled(Boolean(asset && hasChipNumbers(asset.graph)));
+    this.auditionButton.setEnabled(Boolean(asset));
     this.keyboard.setEnabled(Boolean(asset));
     if (!asset) this.keyboard.releaseAll();
     this.keyboard.setSounding(new Set(this.soundingNotes()));
     this.syncParams(asset);
+    this.followEdits(asset);
+  }
+
+  /** With Audition on, a change to the graph shown is heard once it rests; another asset shown is not a change. */
+  private followEdits(asset: InstrumentAsset | null): void {
+    const print = asset ? soundPrint(asset) : '';
+    const changed = (asset?.id ?? '') === this.heardFor && print !== this.heard;
+    this.heard = print;
+    this.heardFor = asset?.id ?? '';
+    if (!changed || !this.auditionButton.toggled) return;
+    clearTimeout(this.auditionTimer);
+    this.auditionTimer = setTimeout(() => this.audition(), AUDITION_DELAY_MS);
   }
 
   private syncOctave(): void {
@@ -186,3 +304,9 @@ export class InstrumentEditor extends AssetTabEditor<InstrumentAsset, GraphCanva
     for (const [name, field] of this.paramFields) field.setNumber(this.values[name] ?? 0);
   }
 }
+
+/** How a note of the instrument sounds hangs on its nodes' settings and edges, not on where they lie. */
+function soundPrint(asset: InstrumentAsset): string {
+  const { nodes, edges } = asset.graph;
+  return JSON.stringify([nodes.map((n) => [n.id, n.type, n.params]), edges.map((e) => [e.from, e.to])]);
+}

tests/core/chip-presets.test.ts

@@ -0,0 +1,195 @@
+/**
+ * The Preset menu, Randomize and Mutate of the Instrument tab (#329): sfxr's generators worked out
+ * into a Chip, an Envelope, a Filter and a Bitcrusher, and its randomizer and mutator on their numbers.
+ */
+import { describe, expect, it } from 'vitest';
+import { ReplaceGraphCommand } from '../../src/core/commands/graphCommands';
+import { CreateAssetCommand } from '../../src/core/commands/assetCommands';
+import type { Graph, GraphNode } from '../../src/core/graph/Graph';
+import {
+  CHIP_PRESETS,
+  chipPresetGraph,
+  hasChipNumbers,
+  mutatedParams,
+  randomizedParams,
+} from '../../src/core/instrument/chipPresets';
+import { compileInstrument, instrumentSourcesOf } from '../../src/core/instrument/compile';
+import { CHIP_ROWS, ENVELOPE_ROWS, starterInstrumentGraph } from '../../src/core/instrument/nodes';
+import type { InstrumentAsset } from '../../src/core/model/Asset';
+import type { FlatDef } from '../../src/core/properties/PropertySchema';
+import { CRUSH_ROWS, FILTER_ROWS, fxChainOf } from '../../src/core/soundfx/nodes';
+import { makeProject } from '../helpers';
+
+/** A seeded random, so a draw is the same on every run. */
+function seeded(seed = 1): () => number {
+  let state = seed;
+  return () => {
+    state = (state * 1664525 + 1013904223) >>> 0;
+    return state / 2 ** 32;
+  };
+}
+
+const byType = (graph: Graph, type: string) => graph.nodes.find((node) => node.type === type)!;
+const ROWS: Record<string, Record<string, FlatDef<'number'>>> = {
+  InstrumentChip: CHIP_ROWS,
+  InstrumentEnvelope: ENVELOPE_ROWS,
+  SoundFxFilter: FILTER_ROWS,
+  SoundFxBitcrusher: CRUSH_ROWS,
+};
+
+function withinRows(node: GraphNode, keys: string[]): void {
+  for (const key of keys) {
+    const row = ROWS[node.type]![key]!;
+    const value = node.params[key] as number;
+    expect(value, `${node.type}.${key}`).toBeGreaterThanOrEqual(row.min ?? -Infinity);
+    expect(value, `${node.type}.${key}`).toBeLessThanOrEqual(row.max ?? Infinity);
+  }
+}
+
+describe('a preset (#329)', () => {
+  it('is a chain from every note through Chip, Envelope, Filter and Bitcrusher, ending by itself', () => {
+    const sources = instrumentSourcesOf(makeProject().project);
+    for (const { value } of CHIP_PRESETS) {
+      const graph = chipPresetGraph(value, seeded());
+      expect(
+        graph.nodes.map((n) => n.type),
+        value,
+      ).toEqual([
+        'InstrumentNotes',
+        'InstrumentChip',
+        'InstrumentEnvelope',
+        'SoundFxFilter',
+        'SoundFxBitcrusher',
+        'InstrumentOutput',
+      ]);
+      const frequencies = [0, 60, 127].map((note) => {
+        const build = compileInstrument(graph, note, sources);
+        expect(build.reason, value).toBe('');
+        const chain = fxChainOf(build.layers[0]!);
+        expect('chip' in chain && chain.stages.map((s) => s.kind), value).toEqual([
+          'envelope',
+          'pass',
+          'crush',
+        ]);
+        const envelope = chain.stages[0]!;
+        expect(envelope.kind === 'envelope' && envelope.envelope.sustain, value).toBe(0);
+        return 'chip' in chain ? chain.chip?.frequency : undefined;
+      });
+      // Its own frequency on every key, as an sfxr sound has.
+      expect(new Set(frequencies).size, value).toBe(1);
+      withinRows(byType(graph, 'InstrumentChip'), Object.keys(CHIP_ROWS));
+    }
+  });
+
+  it("works sfxr's settings out into Hz and seconds", () => {
+    // At 0 every draw takes the low end: a coin at sfxr's 0.4, no arpeggio, a decay of 0.1.
+    const low = chipPresetGraph('pickup', () => 0);
+    expect(byType(low, 'InstrumentNotes').params).toEqual({ from: '0', to: '127' });
+    expect(byType(low, 'InstrumentChip').params).toMatchObject({
+      wave: 'square',
+      followNote: false,
+      frequency: 568,
+      duty: 0.5,
+      slide: 0,
+      arpeggio: 0,
+    });
+    expect(byType(low, 'InstrumentEnvelope').params).toMatchObject({ attack: 0, decay: 0.068, sustain: 0 });
+    expect(byType(low, 'SoundFxFilter').params).toEqual({ filter: 'lowpass', cutoff: 20000, resonance: 0 });
+    expect(byType(low, 'SoundFxBitcrusher').params).toEqual({ bits: 8, rate: 22050, mix: 1 });
+    // Near 1 the coin jumps up by sfxr's arpeggio: a period 0.676 times as long is about 7 semitones.
+    const high = byType(
+      chipPresetGraph('pickup', () => 0.999),
+      'InstrumentChip',
+    ).params;
+    expect(high).toMatchObject({ frequency: 2858, arpeggio: 7, arpeggioTime: 0.042 });
+    // A laser slides down, an explosion is noise.
+    expect(byType(chipPresetGraph('laser', seeded(3)), 'InstrumentChip').params.slide).toBeLessThan(0);
+    expect(byType(chipPresetGraph('explosion', seeded(3)), 'InstrumentChip').params.wave).toBe('noise');
+  });
+
+  it('is drawn anew every time', () => {
+    const random = seeded(7);
+    const a = byType(chipPresetGraph('laser', random), 'InstrumentChip').params;
+    const b = byType(chipPresetGraph('laser', random), 'InstrumentChip').params;
+    expect(a).not.toEqual(b);
+  });
+
+  it('takes the place of the graph in one step', () => {
+    const f = makeProject();
+    const command = new CreateAssetCommand('instrument', 'Coin');
+    f.stack.execute(command);
+    const instrument = command.asset as InstrumentAsset;
+    const before = instrument.graph.nodes.map((n) => n.id);
+    f.stack.execute(
+      new ReplaceGraphCommand(instrument.id, chipPresetGraph('pickup', seeded()), 'Preset Pickup'),
+    );
+    expect(instrument.graph.nodes).toHaveLength(6);
+    f.stack.undo();
+    expect(instrument.graph.nodes.map((n) => n.id)).toEqual(before);
+  });
+});
+
+describe('Randomize and Mutate (#329)', () => {
+  /** A preset with a parameter fed into the Chip's duty, which neither may touch. */
+  function fedPreset(): Graph {
+    const graph = chipPresetGraph('laser', seeded(5));
+    const chip = byType(graph, 'InstrumentChip');
+    const notes = byType(graph, 'InstrumentNotes');
+    chip.params.wave = 'triangle';
+    chip.params.duty = 0.3;
+    graph.edges.push({
+      id: 'fed',
+      from: { node: notes.id, port: 'velocity' },
+      to: { node: chip.id, port: 'duty' },
+    });
+    byType(graph, 'SoundFxBitcrusher').params.mix = 0.4;
+    byType(graph, 'SoundFxFilter').params.filter = 'highpass';
+    return graph;
+  }
+
+  function apply(graph: Graph, changes: ReturnType<typeof randomizedParams>): void {
+    for (const change of changes)
+      graph.nodes.find((n) => n.id === change.node)!.params[change.key] = change.value;
+  }
+
+  it('Randomize draws only the numbers, held to their rows, and leaves a fed input alone', () => {
+    const graph = fedPreset();
+    const changes = randomizedParams(graph, seeded(11));
+    expect(changes.some((c) => c.key === 'duty')).toBe(false);
+    expect(changes.some((c) => ['wave', 'filter', 'followNote', 'mix', 'from', 'to'].includes(c.key))).toBe(
+      false,
+    );
+    expect(new Set(changes.map((c) => graph.nodes.find((n) => n.id === c.node)!.type))).toEqual(
+      new Set(['InstrumentChip', 'InstrumentEnvelope', 'SoundFxFilter', 'SoundFxBitcrusher']),
+    );
+    apply(graph, changes);
+    const chip = byType(graph, 'InstrumentChip');
+    expect(chip.params).toMatchObject({ wave: 'triangle', duty: 0.3 });
+    withinRows(chip, Object.keys(CHIP_ROWS));
+    withinRows(byType(graph, 'SoundFxBitcrusher'), ['bits', 'rate']);
+    expect(byType(graph, 'SoundFxBitcrusher').params.mix).toBe(0.4);
+    expect(byType(graph, 'SoundFxFilter').params.filter).toBe('highpass');
+    expect(byType(graph, 'InstrumentEnvelope').params.sustain).toBe(0);
+  });
+
+  it('Mutate moves some numbers a little and leaves a 0 at 0', () => {
+    const graph = chipPresetGraph('pickup', () => 0);
+    const chip = byType(graph, 'InstrumentChip');
+    // 0.9 every time: each number moves, by 0.8 of its most.
+    const changes = mutatedParams(graph, () => 0.9);
+    const of = (key: string) => changes.find((c) => c.node === chip.id && c.key === key)?.value;
+    expect(of('frequency')).toBe(Math.round(568 * 2 ** 0.2));
+    expect(of('duty')).toBeCloseTo(0.5 + 0.8 * (0.025 + 0.05), 2);
+    for (const key of ['slide', 'arpeggio', 'repeat', 'minFrequency', 'vibratoDepth'])
+      expect(of(key), key).toBeUndefined();
+    expect(changes.some((c) => c.key === 'sustain')).toBe(false);
+    // Below 0.5 a number stays as it is.
+    expect(mutatedParams(graph, () => 0.1)).toEqual([]);
+  });
+
+  it('find nothing to change in an instrument of Samples', () => {
+    expect(hasChipNumbers(starterInstrumentGraph())).toBe(false);
+    expect(randomizedParams(starterInstrumentGraph())).toEqual([]);
+    expect(hasChipNumbers(chipPresetGraph('blip'))).toBe(true);
+  });
+});

tools/e2e/34-sound.mjs

@@ -1076,6 +1076,93 @@ export async function sound(t) {
   );
   await press('ArrowLeft');
 
+  // 34g-6. Presets (#329): Preset → Laser makes the instrument one Chip through Envelope, Filter and
+  //        Bitcrusher and plays the note last played at once – C4, typed just now. Randomize and
+  //        Mutate play anew; a change only plays with Audition on. Three undos bring the blip back.
+  const insGraph = () =>
+    json(`(() => {
+      const graph = __gm.state.project.assets.find((a) => a.id === ${JSON.stringify(insId)}).graph;
+      const of = (type) => graph.nodes.find((n) => n.type === type)?.params ?? null;
+      return { types: graph.nodes.map((n) => n.type), chip: of('InstrumentChip'), envelope: of('InstrumentEnvelope') };
+    })()`);
+  const clickHook = async (hook) => {
+    const at = await json(`__gm.instrument.${hook}()`);
+    await click(at.x, at.y);
+  };
+  await evaluate('__gm.sound.stopAll()');
+  const beforePreset = await stats();
+  await clickHook('presetAt');
+  const presetMenu = await json('__gm.overlayTexts()');
+  await clickText('Laser');
+  const preset = await waitFor(stats, (s) => s.started > beforePreset.started);
+  const laser = await insGraph();
+  const presetInfo = await json('__gm.instrument.info()');
+  check(
+    'Preset → Laser makes Notes → Chip → Envelope → Filter → Bitcrusher → Output and plays at once',
+    ['Pickup', 'Laser', 'Explosion', 'Powerup', 'Hit', 'Jump', 'Blip'].every((label) =>
+      presetMenu.includes(label),
+    ) &&
+      laser.types.join() ===
+        'InstrumentNotes,InstrumentChip,InstrumentEnvelope,SoundFxFilter,SoundFxBitcrusher,InstrumentOutput' &&
+      laser.chip?.followNote === false &&
+      laser.chip.slide < 0 &&
+      laser.envelope?.sustain === 0 &&
+      preset.last?.file === `instrument:${insId}` &&
+      presetInfo === '128 notes',
+    JSON.stringify({ presetMenu, laser, last: preset.last, presetInfo }),
+  );
+  await shot('34-instrument-preset');
+
+  const beforeRandom = await stats();
+  await clickHook('randomizeAt');
+  const randomized = await waitFor(stats, (s) => s.started > beforeRandom.started);
+  const drawn = await insGraph();
+  await clickHook('mutateAt');
+  const mutated = await waitFor(stats, (s) => s.started > randomized.started);
+  const moved = await insGraph();
+  check(
+    'Randomize draws the numbers anew and keeps the wave, Mutate moves some; both play at once',
+    randomized.started > beforeRandom.started &&
+      drawn.chip?.wave === laser.chip.wave &&
+      drawn.chip.frequency !== laser.chip.frequency &&
+      mutated.started > randomized.started &&
+      JSON.stringify([moved.chip, moved.envelope]) !== JSON.stringify([drawn.chip, drawn.envelope]),
+    JSON.stringify({ laser: laser.chip, drawn: drawn.chip, moved: moved.chip }),
+  );
+
+  const setFrequency = (hz) =>
+    mutate(`__gm.state.project.assets.find((a) => a.id === ${JSON.stringify(insId)})
+      .graph.nodes.find((n) => n.type === 'InstrumentChip').params.frequency = ${hz}`);
+  await sleep(300);
+  const silent = await stats();
+  await setFrequency(300);
+  await sleep(500);
+  const unheard = await stats();
+  await clickHook('auditionAt');
+  const auditionOn = (await json('__gm.instrument.auditionAt()')).toggled;
+  await setFrequency(400);
+  const auditioned = await waitFor(stats, (s) => s.started > unheard.started);
+  await clickHook('auditionAt');
+  check(
+    'a change to the instrument is heard only with Audition on',
+    unheard.started === silent.started && auditionOn && auditioned.started > unheard.started,
+    JSON.stringify({
+      silent: silent.started,
+      unheard: unheard.started,
+      auditionOn,
+      auditioned: auditioned.started,
+    }),
+  );
+
+  for (let i = 0; i < 3; i++) await t.clickToolbar('undo');
+  const restored = await insGraph();
+  check(
+    'three undos take back Mutate, Randomize and the preset: Notes → Sample → Output again',
+    restored.types.join() === 'InstrumentNotes,InstrumentSample,InstrumentOutput',
+    JSON.stringify(restored.types),
+  );
+  await evaluate('__gm.sound.stopAll()');
+
   await mutate(`
     const graph = __gm.state.project.assets.find((a) => a.id === 'sn-logic').graph;
     graph.nodes.push(${JSON.stringify(