diff --git a/src/editor/agent/catalog/composition.ts b/src/editor/agent/catalog/composition.ts
new file mode 100644
index 00000000..7067469a
--- /dev/null
+++ b/src/editor/agent/catalog/composition.ts
@@ -0,0 +1,387 @@
+import { CommandError } from '../../../core/commands/Command';
+import {
+  addCompositionItem,
+  removeCompositionTrack,
+  removeFromComposition,
+  SetCompositionCommand,
+} from '../../../core/commands/compositionCommands';
+import { addPictureItem, droppedPicture } from '../../../core/commands/compositionSprites';
+import { requireComposition } from '../../../core/commands/require';
+import { newId } from '../../../core/ids';
+import type {
+  CompositionAsset,
+  CompositionClip,
+  CompositionItem,
+  CompositionTrack,
+} from '../../../core/model/Asset';
+import {
+  audioSeconds,
+  clipLength,
+  compositionFps,
+  fittedLength,
+  itemSounds,
+  newCompositionTrack,
+} from '../../../core/model/composition';
+import {
+  audioKindOf,
+  clipSpans,
+  droppedLength,
+  fadedItem,
+  movedWithClips,
+  resizedItem,
+} from '../../../core/model/compositionEdit';
+import { placementRejection } from '../../../core/model/placement';
+import { findAsset, findAssetOf, type Project } from '../../../core/model/Project';
+import { FADE_CURVES, type FadeCurve } from '../../../core/model/sound';
+import { MASTER_BUS, TO_COMPOSITION_BUS } from '../../../core/properties/buses';
+import { ITEM_MIN_DB, SOUND_ITEM_MAX_DB } from '../../../core/music/song';
+import type { ArgSchema } from '../argCheck';
+import {
+  type Args,
+  type CatalogCommand,
+  flag,
+  id,
+  ids,
+  number,
+  numberOf,
+  object,
+  oneOf,
+  text,
+  theTab,
+  whole,
+} from './shared';
+
+const COMPOSITION = id('Id of the composition asset.');
+const TRACK = id('Id of the track, as get_asset lists it under tracks.');
+const ITEM = id('Id of the item, as get_asset lists it under items.');
+const CLIP = id('Id of the clip, as get_asset lists it under clips.');
+const INDEX = whole('Place in the list of tracks, from 0 (the top one, drawn in front).', 0);
+const FRAME = whole('Frames from the start, at the fps of the composition.', 0);
+const CURVE = oneOf(
+  FADE_CURVES.map((c) => c.value),
+  'The shape of the fade.',
+);
+const BUS: ArgSchema = {
+  type: 'string',
+  description:
+    `Where an audio item is heard: "${TO_COMPOSITION_BUS}" into the bus of the composition, "" along the routing ` +
+    `of what it plays, "${MASTER_BUS}" the master, else the id of a bus.`,
+};
+
+/** The tracks, items and animation clips of Composition assets. */
+export const COMPOSITION_COMMANDS: readonly CatalogCommand[] = [
+  {
+    name: 'add_composition_track',
+    description:
+      'Adds a track to a composition, at the bottom or at an index. The top track is drawn in front.',
+    args: object({ asset: COMPOSITION, name: id('Its name.'), at: INDEX }, ['asset']),
+    build: (args, { project }) => {
+      const comp = requireComposition(project, text(args, 'asset'));
+      const track = newCompositionTrack(comp.tracks.length + 1);
+      if (typeof args.name === 'string') track.name = args.name;
+      const tracks = [...comp.tracks];
+      tracks.splice(Math.min((args.at as number | undefined) ?? tracks.length, tracks.length), 0, track);
+      return { command: new SetCompositionCommand(comp.id, { tracks }, 'Add track'), made: { id: track.id } };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'change_composition_track',
+    description: 'Renames a track of a composition.',
+    args: object({ asset: COMPOSITION, track: TRACK, name: id('Its name.') }, ['asset', 'track', 'name']),
+    build: (args, { project }) => {
+      const comp = requireComposition(project, text(args, 'asset'));
+      const track = requireTrack(comp, text(args, 'track'));
+      const tracks = comp.tracks.map((t): CompositionTrack =>
+        t === track ? { ...t, name: text(args, 'name') } : t,
+      );
+      return { command: new SetCompositionCommand(comp.id, { tracks }, 'Rename track') };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'move_composition_track',
+    description: 'Moves a track of a composition to another place in its list; what lies on it goes along.',
+    args: object({ asset: COMPOSITION, track: TRACK, to: INDEX }, ['asset', 'track', 'to']),
+    build: (args, { project }) => {
+      const comp = requireComposition(project, text(args, 'asset'));
+      const track = requireTrack(comp, text(args, 'track'));
+      const tracks = comp.tracks.filter((t) => t !== track);
+      tracks.splice(Math.min(numberOf(args, 'to'), tracks.length), 0, track);
+      return { command: new SetCompositionCommand(comp.id, { tracks }, 'Move track') };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'remove_composition_track',
+    description:
+      'Removes a track of a composition with its items, their objects and its clips; the last track stays.',
+    args: object({ asset: COMPOSITION, track: TRACK }, ['asset', 'track']),
+    build: (args, { project }) => {
+      const comp = requireComposition(project, text(args, 'asset'));
+      const track = requireTrack(comp, text(args, 'track'));
+      if (comp.tracks.length <= 1) throw new CommandError('A composition keeps at least one track');
+      return { command: removeCompositionTrack(project, comp.id, track.id) };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'add_composition_item',
+    description:
+      'Lays an asset on a track of a composition, from a frame. A placeable asset (a sprite, a container, a text, ...) ' +
+      'becomes an object of the composition, living as long as the item; a texture, pixel art, vector art, a video or a ' +
+      'clip of one gets a sprite of the composition to wear it; a sound, a sound clip, a pattern or a song becomes an ' +
+      'audio item. Without a length it is as long as its video or what it plays, else 3 s, and keeps following it. ' +
+      "An item's object is moved and set with the commands of area objects, in = the composition. Items of a track may " +
+      'overlap. Animations go on a track with add_composition_clip.',
+    args: object(
+      {
+        asset: COMPOSITION,
+        track: TRACK,
+        place: id('Id of the asset (or video or sound clip) to lay on the track.'),
+        start: FRAME,
+        length: whole('Frames it lasts.', 1),
+        offset: number('Seconds into its video or what it plays it begins.'),
+      },
+      ['asset', 'track', 'place', 'start'],
+    ),
+    build: (args, { project }) => {
+      const comp = requireComposition(project, text(args, 'asset'));
+      requireTrack(comp, text(args, 'track'));
+      const placed = text(args, 'place');
+      const fits = typeof args.length !== 'number';
+      const item: Omit<CompositionItem, 'id'> = {
+        track: text(args, 'track'),
+        start: numberOf(args, 'start'),
+        length: 1,
+        offset: (args.offset as number | undefined) ?? 0,
+        ...(fits ? { fitMedia: true } : {}),
+      };
+      const audio = audioKindOf(project, placed);
+      if (audio) {
+        if (
+          fits &&
+          audio === 'sound' &&
+          audioSeconds(project, { kind: audio, asset: placed, volume: 0, bus: '' }) <= 0
+        )
+          throw new CommandError(
+            `The length of ${findAsset(project, placed)?.name ?? placed} is not known yet – give a length ` +
+              `(${compositionFps(comp)} frames a second)`,
+          );
+        const added: CompositionItem = {
+          ...item,
+          id: newId(),
+          audio: { kind: audio, asset: placed, volume: 0, bus: TO_COMPOSITION_BUS },
+        };
+        added.length = fits ? fittedLength(project, comp, added) : numberOf(args, 'length');
+        const items = [...comp.items, added];
+        return { command: new SetCompositionCommand(comp.id, { items }, 'Add item'), made: { id: added.id } };
+      }
+      const asset = findAsset(project, placed);
+      if (asset?.type === 'animation')
+        throw new CommandError('An animation goes on a track as a clip – use add_composition_clip');
+      const picture = droppedPicture(project, placed);
+      if (!picture) {
+        if (!asset) throw new CommandError(`There is no asset ${placed}`);
+        const rejection = placementRejection(project, comp, asset);
+        if (rejection) throw new CommandError(rejection);
+      }
+      item.length = fits ? droppedLength(project, comp, placed) : numberOf(args, 'length');
+      const { command, objectId } = picture
+        ? addPictureItem(project, comp.id, picture, item)
+        : addCompositionItem(project, comp.id, placed, item);
+      return { command, made: { id: objectId } };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'change_composition_item',
+    description:
+      'Changes an item of a composition. Moving it (start, track) takes the clips that belong to it along. A length ' +
+      'given is its own from then on; fitMedia true hands it back to its video or what it plays. Fades are in frames; ' +
+      'volume and bus are for audio items. Give only what changes.',
+    args: object(
+      {
+        asset: COMPOSITION,
+        item: ITEM,
+        track: TRACK,
+        start: FRAME,
+        length: whole('Frames it lasts.', 1),
+        fitMedia: flag('Its length follows its video or what it plays again.'),
+        offset: number('Seconds into its video or what it plays it begins; below 0 it waits that long.'),
+        fadeIn: whole('Frames its sound rises from silence at its start; 0 for none.', 0),
+        fadeOut: whole('Frames its sound falls back to silence at its end; 0 for none.', 0),
+        curveIn: CURVE,
+        curveOut: CURVE,
+        volume: { type: 'number', description: `In dB, from ${ITEM_MIN_DB} to ${SOUND_ITEM_MAX_DB}.` },
+        bus: BUS,
+      },
+      ['asset', 'item'],
+    ),
+    build: (args, { project }) => {
+      const comp = requireComposition(project, text(args, 'asset'));
+      const item = requireItem(comp, text(args, 'item'));
+      let parts: { items: CompositionItem[]; clips?: CompositionClip[] } = { items: [...comp.items] };
+      if (typeof args.start === 'number' || typeof args.track === 'string') {
+        const trackIds = comp.tracks.map((t) => t.id);
+        const by =
+          typeof args.track === 'string'
+            ? trackIds.indexOf(requireTrack(comp, args.track).id) - trackIds.indexOf(item.track)
+            : 0;
+        const moved = movedWithClips(
+          comp.items,
+          comp.clips,
+          new Set([item.id]),
+          trackIds,
+          typeof args.start === 'number' ? args.start - item.start : 0,
+          by,
+          (clip) => Math.max(1, clipLength(project, comp, clip)),
+        );
+        if (!moved)
+          throw new CommandError('A clip that goes along with the item would lie over another clip there');
+        parts = moved;
+      }
+      const at = parts.items.findIndex((i) => i.id === item.id);
+      parts.items[at] = changedItem(project, comp, parts.items[at]!, args);
+      return { command: new SetCompositionCommand(comp.id, parts, 'Change item') };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'remove_composition_items',
+    description:
+      'Removes items of a composition with their objects and the clips that belong to them, and clips.',
+    args: object({ asset: COMPOSITION, items: ids('Ids of the items.'), clips: ids('Ids of the clips.') }, [
+      'asset',
+    ]),
+    build: (args, { project }) => {
+      const comp = requireComposition(project, text(args, 'asset'));
+      const items = (args.items ?? []) as string[];
+      const clips = (args.clips ?? []) as string[];
+      if (items.length + clips.length === 0) throw new CommandError('Name items or clips to remove');
+      for (const itemId of items) requireItem(comp, itemId);
+      for (const clipId of clips) requireClip(comp, clipId);
+      return { command: removeFromComposition(project, comp.id, items, clips) };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'add_composition_clip',
+    description:
+      'Lays an animation on a track of a composition as a clip, one pass long, from a frame. It plays on every item ' +
+      'of its track it overlaps; its rows find their targets in the item as Play animation finds them. Clips of a ' +
+      'track never overlap.',
+    args: object(
+      { asset: COMPOSITION, track: TRACK, animation: id('Id of the animation asset.'), start: FRAME },
+      ['asset', 'track', 'animation', 'start'],
+    ),
+    build: (args, { project }) => {
+      const comp = requireComposition(project, text(args, 'asset'));
+      requireTrack(comp, text(args, 'track'));
+      const animation = findAssetOf(project, text(args, 'animation'), 'animation');
+      if (!animation) throw new CommandError(`${text(args, 'animation')} is no animation asset`);
+      const clip: CompositionClip = {
+        id: newId(),
+        track: text(args, 'track'),
+        animation: animation.id,
+        start: numberOf(args, 'start'),
+      };
+      if (clipLength(project, comp, clip) === 0)
+        throw new CommandError(`${animation.name} has no frames to play here`);
+      requireRoom(project, comp, clip);
+      return {
+        command: new SetCompositionCommand(comp.id, { clips: [...comp.clips, clip] }, 'Add clip'),
+        made: { id: clip.id },
+      };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'change_composition_clip',
+    description: 'Moves a clip of a composition to another frame or track, where it fits whole.',
+    args: object({ asset: COMPOSITION, clip: CLIP, track: TRACK, start: FRAME }, ['asset', 'clip']),
+    build: (args, { project }) => {
+      const comp = requireComposition(project, text(args, 'asset'));
+      const clip = requireClip(comp, text(args, 'clip'));
+      const moved: CompositionClip = {
+        ...clip,
+        ...(typeof args.track === 'string' ? { track: requireTrack(comp, args.track).id } : {}),
+        ...(typeof args.start === 'number' ? { start: args.start } : {}),
+      };
+      requireRoom(project, comp, moved);
+      const clips = comp.clips.map((c) => (c === clip ? moved : c));
+      return { command: new SetCompositionCommand(comp.id, { clips }, 'Move clip') };
+    },
+    shows: theTab,
+  },
+];
+
+/** The item with what `args` change besides its place, refused where it asks for what the item cannot have. */
+function changedItem(
+  project: Project,
+  comp: CompositionAsset,
+  item: CompositionItem,
+  args: Args,
+): CompositionItem {
+  let out = item;
+  if (typeof args.offset === 'number') out = { ...out, offset: args.offset };
+  if (typeof args.length === 'number') out = resizedItem(out, args.length);
+  if (args.fitMedia === true) out = { ...out, fitMedia: true, length: fittedLength(project, comp, out) };
+  if (args.fitMedia === false) out = resizedItem(out, out.length);
+  const fades = ['fadeIn', 'fadeOut', 'curveIn', 'curveOut'].some((key) => args[key] !== undefined);
+  if (fades && !itemSounds(project, comp, out))
+    throw new CommandError(
+      'Only an item with a sound fades: an audio item, or one whose object wears a video',
+    );
+  if (typeof args.fadeIn === 'number') out = fadedItem(out, 'in', out.start + args.fadeIn);
+  if (typeof args.fadeOut === 'number') out = fadedItem(out, 'out', out.start + out.length - args.fadeOut);
+  if (typeof args.curveIn === 'string') out = { ...out, curveIn: args.curveIn as FadeCurve };
+  if (typeof args.curveOut === 'string') out = { ...out, curveOut: args.curveOut as FadeCurve };
+  if (args.volume !== undefined || args.bus !== undefined) {
+    if (!out.audio) throw new CommandError('Only an audio item has a volume and a bus');
+    const audio = { ...out.audio };
+    if (typeof args.volume === 'number') {
+      if (args.volume < ITEM_MIN_DB || args.volume > SOUND_ITEM_MAX_DB)
+        throw new CommandError(`The volume has to be from ${ITEM_MIN_DB} to ${SOUND_ITEM_MAX_DB}`);
+      audio.volume = args.volume;
+    }
+    if (typeof args.bus === 'string') audio.bus = busOf(project, args.bus);
+    out = { ...out, audio };
+  }
+  return out;
+}
+
+function busOf(project: Project, bus: string): string {
+  if (bus === '' || bus === TO_COMPOSITION_BUS || bus === MASTER_BUS) return bus;
+  if (findAsset(project, bus)?.type !== 'bus') throw new CommandError(`${bus} is no bus asset`);
+  return bus;
+}
+
+/** Refuses a clip that would lie over another clip of its track. */
+function requireRoom(project: Project, comp: CompositionAsset, clip: CompositionClip): void {
+  const length = Math.max(1, clipLength(project, comp, clip));
+  const taken = clipSpans(comp.clips, clip.track, (c) => clipLength(project, comp, c), new Set([clip.id]));
+  const hit = taken.find((span) => span.start < clip.start + length && clip.start < span.start + span.length);
+  if (hit)
+    throw new CommandError(
+      `The clip (${length} frames from ${clip.start}) would lie over the one at ${hit.start}–${hit.start + hit.length}`,
+    );
+}
+
+function requireTrack(comp: CompositionAsset, trackId: string): CompositionTrack {
+  const track = comp.tracks.find((t) => t.id === trackId);
+  if (!track) throw new CommandError(`${comp.name} has no track ${trackId}`);
+  return track;
+}
+
+function requireItem(comp: CompositionAsset, itemId: string): CompositionItem {
+  const item = comp.items.find((i) => i.id === itemId);
+  if (!item) throw new CommandError(`${comp.name} has no item ${itemId}`);
+  return item;
+}
+
+function requireClip(comp: CompositionAsset, clipId: string): CompositionClip {
+  const clip = comp.clips.find((c) => c.id === clipId);
+  if (!clip) throw new CommandError(`${comp.name} has no clip ${clipId}`);
+  return clip;
+}
diff --git a/src/editor/agent/catalog/music.ts b/src/editor/agent/catalog/music.ts
new file mode 100644
index 00000000..5f42229c
--- /dev/null
+++ b/src/editor/agent/catalog/music.ts
@@ -0,0 +1,548 @@
+import {
+  AddClipCommand,
+  RemoveClipCommand,
+  RenameClipCommand,
+  SetClipPropsCommand,
+} from '../../../core/commands/clipCommands';
+import { type Command, CommandError } from '../../../core/commands/Command';
+import { oneStep } from '../../../core/commands/CompoundCommand';
+import { SetLoopCommand, SetPatternNotesCommand } from '../../../core/commands/patternCommands';
+import { requireAsset, requireEdge, requirePattern, requireSong } from '../../../core/commands/require';
+import { SetSendCommand, SetSongCommand } from '../../../core/commands/songCommands';
+import type { SendTap } from '../../../core/graph/Graph';
+import { newId } from '../../../core/ids';
+import { HIGHEST_NOTE, LOWEST_NOTE, noteName } from '../../../core/instrument/notes';
+import type { PatternAsset, SongAsset } from '../../../core/model/Asset';
+import { audioSeconds } from '../../../core/model/composition';
+import type { PropertyBag } from '../../../core/model/Properties';
+import {
+  findAsset,
+  findAssetOf,
+  findGraphAsset,
+  type Project,
+  ROUTING_ID,
+} from '../../../core/model/Project';
+import { clipsOf, findSound, hasClips } from '../../../core/model/sound';
+import { DEFAULT_VELOCITY, patternLength, type PatternNote } from '../../../core/music/pattern';
+import { SEND_TAPS } from '../../../core/music/routing';
+import {
+  itemMaxDb,
+  ITEM_MIN_DB,
+  MAX_TRANSPOSE,
+  newItem,
+  newTrack,
+  type SongItem,
+  type SongTrack,
+  songMeter,
+  songTempo,
+  TRACK_MAX_DB,
+  TRACK_MIN_DB,
+} from '../../../core/music/song';
+import { TICKS_PER_QUARTER, ticksOfSeconds, ticksPerBar } from '../../../core/music/time';
+import { NO_FX } from '../../../core/properties/assetFx';
+import type { ArgSchema } from '../argCheck';
+import {
+  type Args,
+  type CatalogCommand,
+  flag,
+  id,
+  ids,
+  listOf,
+  number,
+  numberOf,
+  object,
+  oneOf,
+  text,
+  theTab,
+  whole,
+} from './shared';
+
+const PATTERN = id('Id of the pattern asset.');
+const SONG = id('Id of the song asset.');
+const TRACK = id('Id of the track, as get_asset lists it under tracks.');
+const ITEM = id('Id of the item, as get_asset lists it under items.');
+const INDEX = whole('Place in the list of tracks, from 0 (the top).', 0);
+const TICK = whole(`Ticks from the start; ${TICKS_PER_QUARTER} to a quarter note.`, 0);
+const NOTE: ArgSchema = {
+  description: 'The pitch: a MIDI number (60 is C4) or a name with sharps only, like "C4", "F#3", "A-1".',
+};
+const VELOCITY: ArgSchema = { type: 'number', minimum: 0, maximum: 1, description: 'How hard, 0 to 1.' };
+const FX: ArgSchema = { type: 'string', description: 'Id of a Sound FX asset, or "" for none.' };
+const DB = (description: string): ArgSchema => ({ type: 'number', description: `${description} In dB.` });
+
+/** Notes of patterns, loops, the tracks and items of songs, sends of a routing, clips of sounds and videos. */
+export const MUSIC_COMMANDS: readonly CatalogCommand[] = [
+  {
+    name: 'add_notes',
+    description:
+      `Adds notes to a pattern; with replace, they take the place of all its notes. Time is in ticks, ${TICKS_PER_QUARTER} ` +
+      'to a quarter note; how many bars long the pattern is, its meter, grid, tempo and instrument are properties. ' +
+      'A note has to start before the end of the pattern.',
+    args: object(
+      {
+        asset: PATTERN,
+        notes: {
+          type: 'array',
+          minItems: 1,
+          items: object(
+            { tick: TICK, length: whole('Ticks it is held.', 1), note: NOTE, velocity: VELOCITY },
+            ['tick', 'length', 'note'],
+          ),
+          description: 'The notes.',
+        },
+        replace: flag('Take away the notes it had.'),
+      },
+      ['asset', 'notes'],
+    ),
+    build: (args, { project }) => {
+      const pattern = requirePattern(project, text(args, 'asset'));
+      const added = (args.notes as Args[]).map((n): PatternNote => ({
+        id: newId(),
+        tick: n.tick as number,
+        length: n.length as number,
+        note: pitchOf(n.note),
+        velocity: (n.velocity as number | undefined) ?? DEFAULT_VELOCITY,
+      }));
+      for (const note of added) requireInside(pattern, note);
+      const notes = [...(args.replace === true ? [] : pattern.notes), ...added];
+      const command = new SetPatternNotesCommand(pattern.id, notes, 'Add notes');
+      return added.length === 1 ? { command, made: { id: added[0]!.id } } : { command };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'change_notes',
+    description:
+      'Changes notes of a pattern by their ids: where they start, how long, the pitch, the velocity.',
+    args: object(
+      {
+        asset: PATTERN,
+        notes: {
+          type: 'array',
+          minItems: 1,
+          items: object(
+            {
+              id: id('Id of the note.'),
+              tick: TICK,
+              length: whole('Ticks it is held.', 1),
+              note: NOTE,
+              velocity: VELOCITY,
+            },
+            ['id'],
+          ),
+          description: 'Each with only what changes.',
+        },
+      },
+      ['asset', 'notes'],
+    ),
+    build: (args, { project }) => {
+      const pattern = requirePattern(project, text(args, 'asset'));
+      const changes = new Map((args.notes as Args[]).map((n) => [n.id as string, n]));
+      for (const noteId of changes.keys())
+        if (!pattern.notes.some((n) => n.id === noteId))
+          throw new CommandError(`${pattern.name} has no note ${noteId}`);
+      const notes = pattern.notes.map((note) => {
+        const change = changes.get(note.id);
+        if (!change) return note;
+        const changed: PatternNote = {
+          ...note,
+          ...(typeof change.tick === 'number' ? { tick: change.tick } : {}),
+          ...(typeof change.length === 'number' ? { length: change.length } : {}),
+          ...(change.note === undefined ? {} : { note: pitchOf(change.note) }),
+          ...(typeof change.velocity === 'number' ? { velocity: change.velocity } : {}),
+        };
+        requireInside(pattern, changed);
+        return changed;
+      });
+      return { command: new SetPatternNotesCommand(pattern.id, notes, 'Change notes') };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'remove_notes',
+    description: 'Removes notes of a pattern by their ids.',
+    args: object({ asset: PATTERN, notes: ids('Ids of the notes.') }, ['asset', 'notes']),
+    build: (args, { project }) => {
+      const pattern = requirePattern(project, text(args, 'asset'));
+      const going = new Set(listOf(args, 'notes'));
+      for (const noteId of going)
+        if (!pattern.notes.some((n) => n.id === noteId))
+          throw new CommandError(`${pattern.name} has no note ${noteId}`);
+      const notes = pattern.notes.filter((n) => !going.has(n.id));
+      return { command: new SetPatternNotesCommand(pattern.id, notes, 'Delete notes') };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'set_loop',
+    description:
+      'Sets the loop the playhead of a pattern or a song runs round, in ticks; leave start and end out to loop the whole.',
+    args: object({ asset: id('Id of the pattern or song asset.'), start: TICK, end: whole('Ticks.', 1) }, [
+      'asset',
+    ]),
+    build: (args, { project }) => {
+      const asset = requireAsset(project, text(args, 'asset'));
+      if (asset.type !== 'pattern' && asset.type !== 'song')
+        throw new CommandError(`${asset.name} is no pattern or song`);
+      const given = [args.start, args.end].filter((value) => value !== undefined).length;
+      if (given === 1) throw new CommandError('Give start and end, or neither for the whole');
+      const loop = given === 0 ? null : { start: numberOf(args, 'start'), end: numberOf(args, 'end') };
+      if (loop && loop.end <= loop.start) throw new CommandError('The loop has to end after it starts');
+      return { command: new SetLoopCommand(asset.type, asset.id, loop) };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'add_song_track',
+    description:
+      'Adds a track to a song, at the bottom or at an index. Its routing gets a node for it, going to the output.',
+    args: object({ asset: SONG, name: id('Its name.'), at: INDEX }, ['asset']),
+    build: (args, { project }) => {
+      const song = requireSong(project, text(args, 'asset'));
+      const track = newTrack(song.tracks.length + 1);
+      if (typeof args.name === 'string') track.name = args.name;
+      const tracks = [...song.tracks];
+      tracks.splice(Math.min((args.at as number | undefined) ?? tracks.length, tracks.length), 0, track);
+      return { command: new SetSongCommand(song.id, { tracks }, 'Add track'), made: { id: track.id } };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'change_song_track',
+    description: 'Changes a track of a song. Give only what changes.',
+    args: object(
+      {
+        asset: SONG,
+        track: TRACK,
+        name: id('Its name.'),
+        volume: DB(`From ${TRACK_MIN_DB} to ${TRACK_MAX_DB}.`),
+        pan: number('-1 all left, 1 all right.'),
+        mute: flag('Muted.'),
+        solo: flag('Soloed.'),
+        fx: {
+          ...FX,
+          description: 'Id of the Sound FX everything on the track goes through, or "" for none.',
+        },
+      },
+      ['asset', 'track'],
+    ),
+    build: (args, { project }) => {
+      const song = requireSong(project, text(args, 'asset'));
+      const track = requireTrack(song, text(args, 'track'));
+      const changed: SongTrack = { ...track };
+      if (typeof args.name === 'string') changed.name = args.name;
+      if (typeof args.volume === 'number')
+        changed.volume = within(args.volume, TRACK_MIN_DB, TRACK_MAX_DB, 'volume');
+      if (typeof args.pan === 'number') changed.pan = within(args.pan, -1, 1, 'pan');
+      if (typeof args.mute === 'boolean') changed.mute = args.mute;
+      if (typeof args.solo === 'boolean') changed.solo = args.solo;
+      if (typeof args.fx === 'string') changed.fx = soundFxOf(project, args.fx);
+      const tracks = song.tracks.map((t) => (t.id === track.id ? changed : t));
+      return { command: new SetSongCommand(song.id, { tracks }, 'Change track') };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'move_song_track',
+    description: 'Moves a track of a song to another place in its list.',
+    args: object({ asset: SONG, track: TRACK, to: INDEX }, ['asset', 'track', 'to']),
+    build: (args, { project }) => {
+      const song = requireSong(project, text(args, 'asset'));
+      const track = requireTrack(song, text(args, 'track'));
+      const tracks = song.tracks.filter((t) => t.id !== track.id);
+      tracks.splice(Math.min(numberOf(args, 'to'), tracks.length), 0, track);
+      return { command: new SetSongCommand(song.id, { tracks }, 'Move track') };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'remove_song_track',
+    description: 'Removes a track of a song with its items; the last track stays.',
+    args: object({ asset: SONG, track: TRACK }, ['asset', 'track']),
+    build: (args, { project }) => {
+      const song = requireSong(project, text(args, 'asset'));
+      const track = requireTrack(song, text(args, 'track'));
+      if (song.tracks.length <= 1) throw new CommandError('A song keeps at least one track');
+      const parts = {
+        tracks: song.tracks.filter((t) => t.id !== track.id),
+        items: song.items.filter((i) => i.track !== track.id),
+      };
+      return { command: new SetSongCommand(song.id, parts, 'Delete track') };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'add_song_item',
+    description:
+      `Lays a pattern, a sound or a clip of a sound on a track of a song. Time is in ticks of the song, ${TICKS_PER_QUARTER} ` +
+      'to a quarter note at its tempo. Without a length it is as long as its pattern, or its sound at the tempo of the ' +
+      'song; a pattern item repeats its pattern for as long as it lasts.',
+    args: object(
+      {
+        asset: SONG,
+        track: TRACK,
+        play: id('Id of the pattern, sound or sound clip.'),
+        tick: TICK,
+        ...itemFields(),
+      },
+      ['asset', 'track', 'play', 'tick'],
+    ),
+    build: (args, { project }) => {
+      const song = requireSong(project, text(args, 'asset'));
+      requireTrack(song, text(args, 'track'));
+      const play = text(args, 'play');
+      const kind = findAssetOf(project, play, 'pattern')
+        ? 'pattern'
+        : findSound(project, play)
+          ? 'sound'
+          : null;
+      if (!kind) throw new CommandError(`${play} is no pattern, sound or sound clip`);
+      const length = (args.length as number | undefined) ?? itemLength(project, song, kind, play);
+      const item = changedItem(
+        project,
+        newItem({ track: text(args, 'track'), kind, asset: play, tick: numberOf(args, 'tick'), length }),
+        args,
+      );
+      return {
+        command: new SetSongCommand(song.id, { items: [...song.items, item] }, 'Add item'),
+        made: { id: item.id },
+      };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'change_song_item',
+    description:
+      'Changes an item of a song: its track, where it starts, how long, and how it plays. Give only what changes.',
+    args: object({ asset: SONG, item: ITEM, track: TRACK, tick: TICK, ...itemFields() }, ['asset', 'item']),
+    build: (args, { project }) => {
+      const song = requireSong(project, text(args, 'asset'));
+      const item = song.items.find((i) => i.id === text(args, 'item'));
+      if (!item) throw new CommandError(`${song.name} has no item ${text(args, 'item')}`);
+      if (typeof args.track === 'string') requireTrack(song, args.track);
+      const changed = changedItem(project, item, args);
+      const items = song.items.map((i) => (i.id === item.id ? changed : i));
+      return { command: new SetSongCommand(song.id, { items }, 'Change item') };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'remove_song_items',
+    description: 'Removes items of a song.',
+    args: object({ asset: SONG, items: ids('Ids of the items.') }, ['asset', 'items']),
+    build: (args, { project }) => {
+      const song = requireSong(project, text(args, 'asset'));
+      const going = new Set(listOf(args, 'items'));
+      for (const itemId of going)
+        if (!song.items.some((i) => i.id === itemId))
+          throw new CommandError(`${song.name} has no item ${itemId}`);
+      const items = song.items.filter((i) => !going.has(i.id));
+      return {
+        command: new SetSongCommand(song.id, { items }, going.size === 1 ? 'Delete item' : 'Delete items'),
+      };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'set_send',
+    description:
+      `How loud a link of a song's routing or of the master routing (asset "${ROUTING_ID}") sends, and where it taps: ` +
+      'post (after volume and pan), postFx (after the sound FX, before volume and pan) or preFx (before the sound FX). ' +
+      'In the master routing only a bus or a song taps anywhere but post. Links are drawn with connect.',
+    args: object(
+      {
+        asset: id(`Id of the song, or "${ROUTING_ID}".`),
+        edge: id('Id of the link, as get_graph lists it.'),
+        volume: DB(`From ${TRACK_MIN_DB} to ${TRACK_MAX_DB}.`),
+        tap: oneOf(
+          SEND_TAPS.map((t) => t.value),
+          'Where it taps.',
+        ),
+      },
+      ['asset', 'edge'],
+    ),
+    build: (args, { project }) => {
+      const holder = findGraphAsset(project, text(args, 'asset'));
+      if (holder?.type !== 'song' && holder?.type !== 'routing')
+        throw new CommandError(`${text(args, 'asset')} is no song and no master routing`);
+      const edge = requireEdge(project, holder.id, text(args, 'edge'));
+      const volume =
+        typeof args.volume === 'number'
+          ? within(args.volume, TRACK_MIN_DB, TRACK_MAX_DB, 'volume')
+          : (edge.send?.volume ?? 0);
+      const tap = (args.tap as SendTap | undefined) ?? edge.send?.tap ?? 'post';
+      return { command: new SetSendCommand(holder.id, edge.id, { volume, tap }) };
+    },
+    shows: (args) => ({ kind: 'nodes', asset: text(args, 'asset'), ids: [] }),
+  },
+  {
+    name: 'add_clip',
+    description:
+      'Adds a clip to a sound or a video: a stretch of its file with a name, which a song, a composition, a Play ' +
+      'sound node or a sprite can play instead of the whole. props are its rows by key (get_asset lists them as ' +
+      'clipProperties): start and end in seconds (end 0 is the end of the file), and on a sound reverse and its fades.',
+    args: object(
+      {
+        asset: id('Id of the sound or video asset.'),
+        name: id('Its name; else Clip 1, Clip 2, ...'),
+        props: { type: 'object', description: 'Its rows by key.' },
+      },
+      ['asset'],
+    ),
+    build: (args) => {
+      const add = new AddClipCommand(text(args, 'asset'), (args.props ?? {}) as PropertyBag);
+      const steps: Command[] = [add];
+      if (typeof args.name === 'string')
+        steps.push(new RenameClipCommand(text(args, 'asset'), add.clipId, args.name));
+      return { command: steps.length === 1 ? add : oneStep('Add clip', steps), made: { id: add.clipId } };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'change_clip',
+    description:
+      'Changes a clip of a sound or a video: its name, and its rows by key. Give only what changes.',
+    args: object(
+      {
+        asset: id('Id of the sound or video asset.'),
+        clip: id('Id of the clip.'),
+        name: id('Its name.'),
+        props: { type: 'object', description: 'Rows by key.' },
+      },
+      ['asset', 'clip'],
+    ),
+    build: (args) => {
+      const steps: Command[] = [];
+      if (typeof args.name === 'string')
+        steps.push(new RenameClipCommand(text(args, 'asset'), text(args, 'clip'), args.name));
+      const props = (args.props ?? {}) as PropertyBag;
+      if (Object.keys(props).length > 0)
+        steps.push(new SetClipPropsCommand(text(args, 'asset'), text(args, 'clip'), props));
+      if (steps.length === 0) throw new CommandError('Name what to change: name or props');
+      return { command: steps.length === 1 ? steps[0]! : oneStep('Change clip', steps) };
+    },
+    shows: theTab,
+  },
+  {
+    name: 'remove_clip',
+    description:
+      'Removes a clip of a sound or a video. What plays it is left naming it and reads as missing until an undo.',
+    args: object({ asset: id('Id of the sound or video asset.'), clip: id('Id of the clip.') }, [
+      'asset',
+      'clip',
+    ]),
+    build: (args, { project }) => {
+      const asset = requireAsset(project, text(args, 'asset'));
+      if (!hasClips(asset) || !clipsOf(asset).some((c) => c.id === text(args, 'clip')))
+        throw new CommandError(`${asset.name} has no clip ${text(args, 'clip')}`);
+      return { command: new RemoveClipCommand(asset.id, text(args, 'clip')) };
+    },
+    shows: theTab,
+  },
+];
+
+/** The fields an item of a song has besides its place. */
+function itemFields(): Record<string, ArgSchema> {
+  return {
+    length: whole('Ticks it lasts.', 1),
+    offset: number('Where in what it plays it starts: ticks into a pattern, seconds into a sound.'),
+    volume: DB(`From ${ITEM_MIN_DB} to 0 for a pattern, to ${itemMaxDb('sound')} for a sound.`),
+    transpose: whole(`Semitones a pattern's notes are moved by, -${MAX_TRANSPOSE} to ${MAX_TRANSPOSE}.`),
+    instrument: {
+      type: 'string',
+      description: "Id of an instrument a pattern plays with instead of its own; '' for its own.",
+    },
+    fx: {
+      type: 'string',
+      description: `Id of a Sound FX it goes through; "" for the one its asset names, "${NO_FX}" for none.`,
+    },
+  };
+}
+
+/** The item with what `args` change, refused where a value is out of range or names the wrong kind of asset. */
+function changedItem(project: Project, item: SongItem, args: Args): SongItem {
+  const out: SongItem = { ...item };
+  if (typeof args.track === 'string') out.track = args.track;
+  if (typeof args.tick === 'number') out.tick = args.tick;
+  if (typeof args.length === 'number') out.length = args.length;
+  if (typeof args.offset === 'number') {
+    if (args.offset < 0) throw new CommandError('The offset has to be 0 or more');
+    out.offset = out.kind === 'pattern' ? Math.round(args.offset) : args.offset;
+  }
+  if (typeof args.volume === 'number')
+    out.volume = within(args.volume, ITEM_MIN_DB, itemMaxDb(out.kind), 'volume');
+  if (typeof args.transpose === 'number') {
+    if (out.kind !== 'pattern') throw new CommandError('Only a pattern item is transposed');
+    out.transpose = within(args.transpose, -MAX_TRANSPOSE, MAX_TRANSPOSE, 'transpose');
+  }
+  if (typeof args.instrument === 'string') {
+    if (out.kind !== 'pattern') throw new CommandError('Only a pattern item plays with an instrument');
+    if (args.instrument !== '' && !findAssetOf(project, args.instrument, 'instrument'))
+      throw new CommandError(`${args.instrument} is no instrument asset`);
+    out.instrument = args.instrument;
+  }
+  if (typeof args.fx === 'string')
+    out.fx = args.fx === NO_FX || args.fx === '' ? args.fx : soundFxOf(project, args.fx);
+  return out;
+}
+
+/** How long an item laid in without a length is: its pattern, or its sound at the song's tempo. */
+function itemLength(project: Project, song: SongAsset, kind: SongItem['kind'], play: string): number {
+  const pattern = kind === 'pattern' ? findAssetOf(project, play, 'pattern') : undefined;
+  if (pattern) return Math.max(1, patternLength(pattern));
+  const seconds = audioSeconds(project, { kind: 'sound', asset: play, volume: 0, bus: '' });
+  if (seconds <= 0)
+    throw new CommandError(
+      `The length of ${findSound(project, play)?.asset.name ?? play} is not known yet – give a length ` +
+        `(a bar of this song is ${ticksPerBar(songMeter(song.props))} ticks)`,
+    );
+  return Math.max(1, Math.round(ticksOfSeconds(seconds, songTempo(song.props))));
+}
+
+function requireTrack(song: SongAsset, trackId: string): SongTrack {
+  const track = song.tracks.find((t) => t.id === trackId);
+  if (!track) throw new CommandError(`${song.name} has no track ${trackId}`);
+  return track;
+}
+
+/** A pitch the agent wrote as a MIDI number or a name like "C#4". */
+export function pitchOf(value: unknown): number {
+  const number =
+    typeof value === 'number'
+      ? value
+      : typeof value === 'string'
+        ? NOTE_BY_NAME.get(value.trim().toUpperCase())
+        : undefined;
+  if (number === undefined || !Number.isInteger(number) || number < LOWEST_NOTE || number > HIGHEST_NOTE)
+    throw new CommandError(
+      `${JSON.stringify(value)} is no note – give ${LOWEST_NOTE} to ${HIGHEST_NOTE} or a name like "C4" or "F#3"`,
+    );
+  return number;
+}
+
+const NOTE_BY_NAME = new Map(
+  Array.from({ length: HIGHEST_NOTE - LOWEST_NOTE + 1 }, (_, i) => [
+    noteName(LOWEST_NOTE + i),
+    LOWEST_NOTE + i,
+  ]),
+);
+
+function requireInside(pattern: PatternAsset, note: PatternNote): void {
+  const end = patternLength(pattern);
+  if (note.tick >= end)
+    throw new CommandError(
+      `A note at tick ${note.tick} lies past the end of ${pattern.name}, which is ${end} ticks long – ` +
+        'give it more bars first',
+    );
+}
+
+function within(value: number, min: number, max: number, what: string): number {
+  if (value < min || value > max) throw new CommandError(`The ${what} has to be from ${min} to ${max}`);
+  return value;
+}
+
+function soundFxOf(project: Project, fx: string): string {
+  if (fx !== '' && findAsset(project, fx)?.type !== 'soundfx')
+    throw new CommandError(`${fx} is no Sound FX asset`);
+  return fx;
+}
diff --git a/src/editor/agent/commandCatalog.ts b/src/editor/agent/commandCatalog.ts
index b97e7874..e5ebe36c 100644
--- a/src/editor/agent/commandCatalog.ts
+++ b/src/editor/agent/commandCatalog.ts
@@ -1,6 +1,8 @@
 import { ANIMATION_COMMANDS } from './catalog/animation';
 import { ASSET_COMMANDS } from './catalog/assets';
+import { COMPOSITION_COMMANDS } from './catalog/composition';
 import { GRAPH_COMMANDS } from './catalog/graphs';
+import { MUSIC_COMMANDS } from './catalog/music';
 import { OBJECT_COMMANDS } from './catalog/objects';
 import { PIXEL_ART_COMMANDS } from './catalog/pixelart';
 import { PROJECT_COMMANDS } from './catalog/project';
@@ -63,6 +65,17 @@ export const AREAS: readonly CommandArea[] = [
     about: 'Shapes of Vector art assets: their outlines, fills, gradients and strokes, groups and layers.',
     commands: VECTOR_ART_COMMANDS,
   },
+  {
+    area: 'music',
+    about:
+      'Notes of patterns; tracks, items and loops of songs; sends of a routing; clips of sounds and videos.',
+    commands: MUSIC_COMMANDS,
+  },
+  {
+    area: 'composition',
+    about: 'Tracks, items and animation clips of Composition assets.',
+    commands: COMPOSITION_COMMANDS,
+  },
   { area: 'project', about: 'Settings of the project as a whole.', commands: PROJECT_COMMANDS },
 ];
 
diff --git a/src/editor/agent/readTools.ts b/src/editor/agent/readTools.ts
index 7687c24e..8a1d836b 100644
--- a/src/editor/agent/readTools.ts
+++ b/src/editor/agent/readTools.ts
@@ -6,6 +6,13 @@ import { ASSET_TYPE_LABELS, ASSET_TYPES, type AssetType, isPlaceableType } from
 import { graphLookup } from '../../core/model/graphLookup';
 import { isTemplateContent, resolveObjects } from '../../core/model/instance';
 import { findAsset, findGraphAsset, type Project } from '../../core/model/Project';
+import { audioSeconds } from '../../core/model/composition';
+import { noteName } from '../../core/instrument/notes';
+import { patternLength } from '../../core/music/pattern';
+import { songLength } from '../../core/music/song';
+import { TICKS_PER_QUARTER } from '../../core/music/time';
+import { CLIP_ROWS } from '../../core/properties/sounds';
+import { VIDEO_CLIP_ROWS } from '../../core/properties/videos';
 import { celOf, paletteColors } from '../../core/model/pixelart';
 import type { CelPixels } from '../../core/model/pixelCel';
 import { objectName } from '../../core/model/SceneObject';
@@ -81,6 +88,19 @@ export function getAsset(project: Project, assetId: string, readCel?: CelLookup)
     plain.colors = paletteColors(project, asset).map(toHex);
     plain.frames = pixelFrames(asset, readCel);
   }
+  if (asset.type === 'pattern') {
+    plain.notes = asset.notes.map((note) => ({ ...note, name: noteName(note.note) }));
+    plain.ticks = { perQuarter: TICKS_PER_QUARTER, length: patternLength(asset) };
+  }
+  if (asset.type === 'song') plain.ticks = { perQuarter: TICKS_PER_QUARTER, length: songLength(asset) };
+  if (asset.type === 'sound' || asset.type === 'video') {
+    plain.clipProperties = (asset.type === 'sound' ? CLIP_ROWS : VIDEO_CLIP_ROWS).map(propertyRow);
+  }
+  if (asset.type === 'sound') {
+    // Known once the editor has loaded it; a song or composition item takes its length from it.
+    const seconds = audioSeconds(project, { kind: 'sound', asset: asset.id, volume: 0, bus: '' });
+    plain.seconds = seconds > 0 ? seconds : 'not loaded';
+  }
   plain.properties = schemaForAsset(project, asset).map(propertyRow);
   return plain;
 }
@@ -169,6 +189,7 @@ export function getGraph(project: Project, assetId: string): object | null {
       from: edge.from,
       to: edge.to,
       ...(edge.label ? { label: edge.label } : {}),
+      ...(edge.send ? { send: edge.send } : {}),
     })),
     groups: (graph.groups ?? []).map(({ text, ...box }) => ({ ...annotationRow(box), title: text })),
     notes: (graph.notes ?? []).map(({ text, ...box }) => ({ ...annotationRow(box), text })),
diff --git a/src/editor/agent/tools.json b/src/editor/agent/tools.json
index 644228b3..1ab73f8a 100644
--- a/src/editor/agent/tools.json
+++ b/src/editor/agent/tools.json
@@ -44,7 +44,7 @@
   {
     "name": "get_asset",
     "title": "Read an asset",
-    "description": "One asset as stored: its property values, the rows of its properties (key, kind, default), the objects of a scene or container with their names and positions (the content of a placed container too, marked fromContainer), what the rows of an animation may aim at (targets), the cells of a small tilemap, the pixels of small pixel art as rows of palette indices (colors as \"#rrggbb\"). A graph is only counted here; read it with get_graph.",
+    "description": "One asset as stored: its property values, the rows of its properties (key, kind, default), the objects of a scene or container with their names and positions (the content of a placed container too, marked fromContainer), what the rows of an animation may aim at (targets), the cells of a small tilemap, the pixels of small pixel art as rows of palette indices (colors as \"#rrggbb\"), the notes of a pattern with their names and how many ticks it is long, the rows a clip of a sound or video has (clipProperties), how many seconds a loaded sound lasts. A graph is only counted here; read it with get_graph.",
     "inputSchema": {
       "type": "object",
       "properties": { "asset": { "type": "string", "description": "Id of the asset." } },
@@ -56,7 +56,7 @@
   {
     "name": "get_graph",
     "title": "Read a graph",
-    "description": "The graph of a behavior, state machine, shader, particles, sound FX or instrument: each node with its settings and its input and output ports as they are now, the edges between ports, and the groups and comments (notes). A node that declares its own ports lists them under ports.",
+    "description": "The graph of a behavior, state machine, shader, particles, sound FX or instrument: each node with its settings and its input and output ports as they are now, the edges between ports (a link of a routing with its send), and the groups and comments (notes). A node that declares its own ports lists them under ports.",
     "inputSchema": {
       "type": "object",
       "properties": { "asset": { "type": "string", "description": "Id of the asset holding the graph." } },
diff --git a/tests/editor/agent-music.test.ts b/tests/editor/agent-music.test.ts
new file mode 100644
index 00000000..50be90e7
--- /dev/null
+++ b/tests/editor/agent-music.test.ts
@@ -0,0 +1,425 @@
+import { afterEach, describe, expect, it } from 'vitest';
+import { CreateSoundCommand } from '../../src/core/commands/assetCommands';
+import type { CompositionAsset, PatternAsset, SongAsset, SoundAsset } from '../../src/core/model/Asset';
+import { setSoundMeasure } from '../../src/core/model/composition';
+import { ROUTING_ID } from '../../src/core/model/Project';
+import { settleRouting } from '../../src/core/music/projectRouting';
+import { TO_COMPOSITION_BUS } from '../../src/core/properties/buses';
+import { runTool } from '../../src/editor/agent/agentTools';
+import { makeSpriteScene, type SceneFixture } from '../helpers';
+import { hostFor, text } from './agentTestHost';
+
+/** The commands of #429 stage 5d: patterns, songs, sends, clips of sounds and compositions. */
+
+const FILE = `${'a7'.repeat(32)}.wav`;
+
+const run = async (fixture: SceneFixture, steps: object[], follows = false) => {
+  const { host, shown } = hostFor(fixture, null, follows);
+  const result = await runTool('run_commands', { steps }, host);
+  return { result, shown, text: text(result) };
+};
+
+const read = async (fixture: SceneFixture, asset: string) =>
+  (await runTool('get_asset', { asset }, hostFor(fixture).host)).structuredContent as Record<string, unknown>;
+
+const graph = async (fixture: SceneFixture, asset: string) =>
+  (await runTool('get_graph', { asset }, hostFor(fixture).host)).structuredContent as {
+    nodes: { id: string; type: string; params: Record<string, unknown> }[];
+    edges: { id: string; from: { node: string }; to: { node: string }; send?: object }[];
+  };
+
+const byId = <T>(fixture: SceneFixture, id: string) => fixture.project.assets.find((a) => a.id === id) as T;
+
+/** Makes the assets by name and gives their ids. */
+async function made<K extends string>(
+  fixture: SceneFixture,
+  assets: Record<K, string>,
+): Promise<Record<K, string>> {
+  const steps = Object.entries(assets).map(([name, type]) => ({
+    command: 'create_asset',
+    args: { type, name },
+    as: name,
+  }));
+  const done = await run(fixture, steps);
+  expect(done.result.isError).toBeUndefined();
+  return Object.fromEntries(
+    Object.keys(assets).map((name) => [name, fixture.project.assets.find((a) => a.name === name)!.id]),
+  ) as Record<K, string>;
+}
+
+function addSound(fixture: SceneFixture, name = 'Blip'): string {
+  const command = new CreateSoundCommand(name, FILE);
+  fixture.stack.execute(command);
+  return command.asset.id;
+}
+
+afterEach(() => setSoundMeasure(() => null));
+
+describe('patterns', () => {
+  it('adds notes by number and by name, reads them back with their names and refuses a note past the end', async () => {
+    const fixture = makeSpriteScene();
+    const { Riff } = await made(fixture, { Riff: 'pattern' });
+    const { result, shown } = await run(
+      fixture,
+      [
+        {
+          command: 'add_notes',
+          args: {
+            asset: Riff,
+            notes: [
+              { tick: 0, length: 480, note: 'C4' },
+              { tick: 480, length: 240, note: 64, velocity: 0.5 },
+              { tick: 960, length: 480, note: 'f#3' },
+            ],
+          },
+        },
+      ],
+      true,
+    );
+    expect(result.isError).toBeUndefined();
+    expect(shown).toEqual([{ kind: 'asset', asset: Riff, open: true }]);
+    const asset = await read(fixture, Riff);
+    expect(asset.ticks).toEqual({ perQuarter: 480, length: 7680 });
+    expect(
+      (asset.notes as Record<string, unknown>[]).map(({ id: _, ...rest }: Record<string, unknown>) => rest),
+    ).toEqual([
+      { tick: 0, length: 480, note: 60, velocity: 0.8, name: 'C4' },
+      { tick: 480, length: 240, note: 64, velocity: 0.5, name: 'E4' },
+      { tick: 960, length: 480, note: 54, velocity: 0.8, name: 'F#3' },
+    ]);
+
+    const past = await run(fixture, [
+      { command: 'add_notes', args: { asset: Riff, notes: [{ tick: 7680, length: 10, note: 60 }] } },
+    ]);
+    expect(past.result.isError).toBe(true);
+    expect(past.text).toContain('7680 ticks long');
+    const flat = await run(fixture, [
+      { command: 'add_notes', args: { asset: Riff, notes: [{ tick: 0, length: 10, note: 'Hb4' }] } },
+    ]);
+    expect(flat.text).toContain('"Hb4" is no note');
+    expect(byId<PatternAsset>(fixture, Riff).notes).toHaveLength(3);
+  });
+
+  it('changes and removes notes by id, replaces all, and sets and clears the loop', async () => {
+    const fixture = makeSpriteScene();
+    const { Riff } = await made(fixture, { Riff: 'pattern' });
+    const added = await run(fixture, [
+      { command: 'add_notes', args: { asset: Riff, notes: [{ tick: 0, length: 120, note: 60 }] }, as: 'n' },
+      { command: 'change_notes', args: { asset: Riff, notes: [{ id: '$n', note: 'G4', tick: 240 }] } },
+      { command: 'add_notes', args: { asset: Riff, notes: [{ tick: 0, length: 60, note: 48 }] }, as: 'm' },
+      { command: 'remove_notes', args: { asset: Riff, notes: ['$m'] } },
+      { command: 'set_loop', args: { asset: Riff, start: 0, end: 1920 } },
+    ]);
+    expect(added.result.isError).toBeUndefined();
+    const pattern = byId<PatternAsset>(fixture, Riff);
+    expect(pattern.notes.map(({ tick, note }) => [tick, note])).toEqual([[240, 67]]);
+    expect(pattern.loop).toEqual({ start: 0, end: 1920 });
+
+    const replaced = await run(fixture, [
+      {
+        command: 'add_notes',
+        args: { asset: Riff, notes: [{ tick: 0, length: 1, note: 0 }], replace: true },
+      },
+      { command: 'set_loop', args: { asset: Riff } },
+    ]);
+    expect(replaced.result.isError).toBeUndefined();
+    expect(byId<PatternAsset>(fixture, Riff).notes.map((n) => n.note)).toEqual([0]);
+    expect(byId<PatternAsset>(fixture, Riff).loop).toBeUndefined();
+    const half = await run(fixture, [{ command: 'set_loop', args: { asset: Riff, start: 0 } }]);
+    expect(half.text).toContain('Give start and end');
+  });
+});
+
+describe('songs', () => {
+  it('lays a pattern as long as it is, a sound by its loaded length, and refuses one not loaded without a length', async () => {
+    const fixture = makeSpriteScene();
+    const { Theme, Riff } = await made(fixture, { Theme: 'song', Riff: 'pattern' });
+    const blip = addSound(fixture);
+    const song = () => byId<SongAsset>(fixture, Theme);
+    const track = song().tracks[0]!.id;
+
+    const unknown = await run(fixture, [
+      { command: 'add_song_item', args: { asset: Theme, track, play: blip, tick: 0 } },
+    ]);
+    expect(unknown.result.isError).toBe(true);
+    expect(unknown.text).toContain('The length of Blip is not known yet');
+    expect(unknown.text).toContain('a bar of this song is 1920 ticks');
+
+    setSoundMeasure(() => 1.25);
+    const laid = await run(fixture, [
+      { command: 'add_song_item', args: { asset: Theme, track, play: Riff, tick: 0, transpose: 12 } },
+      { command: 'add_song_item', args: { asset: Theme, track, play: blip, tick: 7680, volume: 6 } },
+    ]);
+    expect(laid.result.isError).toBeUndefined();
+    // 1.25 s at 120 BPM is 2.5 quarters.
+    expect(
+      song().items.map(({ kind, tick, length, transpose, volume }) => [
+        kind,
+        tick,
+        length,
+        transpose,
+        volume,
+      ]),
+    ).toEqual([
+      ['pattern', 0, 7680, 12, 0],
+      ['sound', 7680, 1200, 0, 6],
+    ]);
+    expect((await read(fixture, blip)).seconds).toBe(1.25);
+
+    const sound = song().items[1]!.id;
+    const wrong = await run(fixture, [
+      { command: 'change_song_item', args: { asset: Theme, item: sound, transpose: 2 } },
+    ]);
+    expect(wrong.text).toContain('Only a pattern item is transposed');
+    const loud = await run(fixture, [
+      { command: 'change_song_item', args: { asset: Theme, item: song().items[0]!.id, volume: 3 } },
+    ]);
+    expect(loud.text).toContain('from -60 to 0');
+  });
+
+  it('adds, changes, moves and removes tracks, keeps the last one, and the routing follows', async () => {
+    const fixture = makeSpriteScene();
+    const { Theme, Riff, Verb } = await made(fixture, { Theme: 'song', Riff: 'pattern', Verb: 'soundfx' });
+    const song = () => byId<SongAsset>(fixture, Theme);
+    const first = song().tracks[0]!.id;
+    const done = await run(fixture, [
+      { command: 'add_song_track', args: { asset: Theme, name: 'Drums', at: 0 }, as: 'drums' },
+      {
+        command: 'change_song_track',
+        args: { asset: Theme, track: '$drums', volume: -6, pan: -0.5, solo: true, fx: Verb },
+      },
+      { command: 'add_song_item', args: { asset: Theme, track: '$drums', play: Riff, tick: 0 } },
+      { command: 'move_song_track', args: { asset: Theme, track: '$drums', to: 1 } },
+    ]);
+    expect(done.result.isError).toBeUndefined();
+    const drums = song().tracks[1]!;
+    expect([song().tracks[0]!.id, drums.name, drums.volume, drums.pan, drums.solo, drums.fx]).toEqual([
+      first,
+      'Drums',
+      -6,
+      -0.5,
+      true,
+      Verb,
+    ]);
+    expect((await graph(fixture, Theme)).nodes).toHaveLength(3);
+
+    const removed = await run(fixture, [
+      { command: 'remove_song_track', args: { asset: Theme, track: drums.id } },
+    ]);
+    expect(removed.result.isError).toBeUndefined();
+    expect(song().items).toHaveLength(0);
+    expect((await graph(fixture, Theme)).nodes).toHaveLength(2);
+    const last = await run(fixture, [{ command: 'remove_song_track', args: { asset: Theme, track: first } }]);
+    expect(last.text).toContain('keeps at least one track');
+    const noFx = await run(fixture, [
+      { command: 'change_song_track', args: { asset: Theme, track: first, fx: Riff } },
+    ]);
+    expect(noFx.text).toContain('is no Sound FX asset');
+  });
+
+  it('sets the send of a song link and of a master routing link, where a sound only sends post', async () => {
+    const fixture = makeSpriteScene();
+    const { Theme } = await made(fixture, { Theme: 'song' });
+    const link = (await graph(fixture, Theme)).edges[0]!.id;
+    const sent = await run(fixture, [
+      { command: 'set_send', args: { asset: Theme, edge: link, volume: -12, tap: 'preFx' } },
+    ]);
+    expect(sent.result.isError).toBeUndefined();
+    expect((await graph(fixture, Theme)).edges[0]!.send).toEqual({ volume: -12, tap: 'preFx' });
+
+    // The editor settles the master routing after every edit; the test host does not, so it is done here.
+    const blip = addSound(fixture);
+    const { Music } = await made(fixture, { Music: 'bus' });
+    settleRouting(fixture.project);
+    const master = fixture.project.routing;
+    // A routed asset's node goes by the asset's id.
+    const linkOf = (asset: string) => master.edges.find((e) => e.from.node === asset)!;
+    const routed = await run(fixture, [
+      { command: 'set_send', args: { asset: ROUTING_ID, edge: linkOf(blip).id, volume: -3, tap: 'preFx' } },
+      { command: 'set_send', args: { asset: ROUTING_ID, edge: linkOf(Music).id, tap: 'postFx' } },
+    ]);
+    expect(routed.result.isError).toBeUndefined();
+    expect([linkOf(blip).send, linkOf(Music).send]).toEqual([
+      { volume: -3, tap: 'post' },
+      { volume: 0, tap: 'postFx' },
+    ]);
+    const blipLink = linkOf(blip).id;
+    const nowhere = await run(fixture, [{ command: 'set_send', args: { asset: blip, edge: blipLink } }]);
+    expect(nowhere.text).toContain('is no song and no master routing');
+  });
+});
+
+describe('clips of sounds', () => {
+  it('adds a clip with a name and its cut, changes it, lists its rows and removes it', async () => {
+    const fixture = makeSpriteScene();
+    const blip = addSound(fixture);
+    const done = await run(fixture, [
+      {
+        command: 'add_clip',
+        args: { asset: blip, name: 'Hit', props: { start: 0.25, end: 0.5 } },
+        as: 'clip',
+      },
+      { command: 'change_clip', args: { asset: blip, clip: '$clip', props: { reverse: true } } },
+    ]);
+    expect(done.result.isError).toBeUndefined();
+    const sound = byId<SoundAsset>(fixture, blip);
+    expect(sound.clips!.map(({ name, props }) => [name, props])).toEqual([
+      ['Hit', { start: 0.25, end: 0.5, reverse: true }],
+    ]);
+    const rows = (await read(fixture, blip)).clipProperties as { key: string }[];
+    expect(rows.map((r) => r.key)).toContain('reverse');
+
+    const bad = await run(fixture, [
+      { command: 'change_clip', args: { asset: blip, clip: sound.clips![0]!.id, props: { start: -1 } } },
+    ]);
+    expect(bad.result.isError).toBe(true);
+    const gone = await run(fixture, [
+      { command: 'remove_clip', args: { asset: blip, clip: sound.clips![0]!.id } },
+    ]);
+    expect(gone.result.isError).toBeUndefined();
+    expect(byId<SoundAsset>(fixture, blip).clips).toEqual([]);
+  });
+});
+
+describe('compositions', () => {
+  it('lays an object, a picture and a pattern on tracks, each as long as the rules say', async () => {
+    const fixture = makeSpriteScene();
+    const { Cut, Riff, Art, Slide } = await made(fixture, {
+      Cut: 'composition',
+      Riff: 'pattern',
+      Art: 'pixelart',
+      Slide: 'animation',
+    });
+    const comp = () => byId<CompositionAsset>(fixture, Cut);
+    const track = comp().tracks[0]!.id;
+    const { result, shown } = await run(
+      fixture,
+      [
+        { command: 'add_composition_track', args: { asset: Cut, name: 'Music' }, as: 'music' },
+        {
+          command: 'add_composition_item',
+          args: { asset: Cut, track, place: fixture.spriteId, start: 0 },
+          as: 'box',
+        },
+        { command: 'add_composition_item', args: { asset: Cut, track, place: Art, start: 30, length: 45 } },
+        { command: 'add_composition_item', args: { asset: Cut, track: '$music', place: Riff, start: 0 } },
+      ],
+      true,
+    );
+    expect(result.isError).toBeUndefined();
+    expect(shown.at(-1)).toEqual({ kind: 'asset', asset: Cut, open: true });
+    const [box, art, riff] = comp().items;
+    // 3 s at 60 fps; a pattern of 4 bars at 120 BPM is 8 s.
+    expect([box!.length, box!.fitMedia, art!.length, art!.fitMedia, riff!.length]).toEqual([
+      180,
+      true,
+      45,
+      undefined,
+      480,
+    ]);
+    expect(riff!.audio).toEqual({ kind: 'pattern', asset: Riff, volume: 0, bus: TO_COMPOSITION_BUS });
+    expect(comp().objects.map((o) => o.id)).toEqual([box!.id, art!.id]);
+    const wearer = fixture.project.assets.find((a) => a.id === comp().objects[1]!.assetId)!;
+    expect([wearer.type, wearer.owner, wearer.props.texture]).toEqual(['sprite', Cut, Art]);
+
+    const animation = await run(fixture, [
+      { command: 'add_composition_item', args: { asset: Cut, track, place: Slide, start: 0 } },
+    ]);
+    expect(animation.text).toContain('use add_composition_clip');
+    const nested = await run(fixture, [
+      { command: 'add_composition_item', args: { asset: Cut, track, place: Cut, start: 0 } },
+    ]);
+    expect(nested.result.isError).toBe(true);
+  });
+
+  it('moves an item with its clip, refuses a clip over another, fades only what sounds, and removes with the object', async () => {
+    const fixture = makeSpriteScene();
+    const { Cut, Riff } = await made(fixture, { Cut: 'composition', Riff: 'pattern' });
+    const anim = await run(fixture, [
+      { command: 'create_asset', args: { type: 'animation', name: 'Slide' }, as: 'anim' },
+      { command: 'set_animation_root', args: { asset: '$anim', root: fixture.spriteId } },
+      { command: 'add_animation_track', args: { asset: '$anim', target: '', property: 'x' }, as: 'row' },
+      { command: 'set_animation_key', args: { asset: '$anim', track: '$row', frame: 0, value: 0 } },
+      { command: 'set_animation_key', args: { asset: '$anim', track: '$row', frame: 30, value: 100 } },
+    ]);
+    expect(anim.result.isError).toBeUndefined();
+    const slide = fixture.project.assets.find((a) => a.name === 'Slide')!.id;
+    const comp = () => byId<CompositionAsset>(fixture, Cut);
+    const track = comp().tracks[0]!.id;
+    const laid = await run(fixture, [
+      {
+        command: 'add_composition_item',
+        args: { asset: Cut, track, place: fixture.spriteId, start: 0, length: 120 },
+        as: 'box',
+      },
+      {
+        command: 'add_composition_clip',
+        args: { asset: Cut, track, animation: slide, start: 10 },
+        as: 'clip',
+      },
+      { command: 'add_composition_item', args: { asset: Cut, track, place: Riff, start: 200 }, as: 'riff' },
+    ]);
+    expect(laid.result.isError).toBeUndefined();
+    const [box, riff] = comp().items;
+
+    const over = await run(fixture, [
+      { command: 'add_composition_clip', args: { asset: Cut, track, animation: slide, start: 30 } },
+    ]);
+    expect(over.text).toContain('would lie over the one at 10');
+
+    const moved = await run(fixture, [
+      { command: 'change_composition_item', args: { asset: Cut, item: box!.id, start: 50 } },
+      {
+        command: 'change_composition_item',
+        args: { asset: Cut, item: riff!.id, fadeIn: 20, volume: -6, bus: '' },
+      },
+    ]);
+    expect(moved.result.isError).toBeUndefined();
+    expect([comp().items[0]!.start, comp().clips[0]!.start]).toEqual([50, 60]);
+    expect(comp().items[1]).toMatchObject({ fadeIn: 20, audio: { volume: -6, bus: '' } });
+
+    const silent = await run(fixture, [
+      { command: 'change_composition_item', args: { asset: Cut, item: box!.id, fadeOut: 5 } },
+    ]);
+    expect(silent.text).toContain('Only an item with a sound fades');
+    const noBus = await run(fixture, [
+      { command: 'change_composition_item', args: { asset: Cut, item: box!.id, volume: -3 } },
+    ]);
+    expect(noBus.text).toContain('Only an audio item');
+
+    const gone = await run(fixture, [
+      { command: 'remove_composition_items', args: { asset: Cut, items: [box!.id] } },
+    ]);
+    expect(gone.result.isError).toBeUndefined();
+    expect([comp().items.map((i) => i.id), comp().objects.length, comp().clips.map((c) => c.id)]).toEqual([
+      [riff!.id],
+      0,
+      [],
+    ]);
+  });
+
+  it('adds, renames, moves and removes tracks, and keeps the last one', async () => {
+    const fixture = makeSpriteScene();
+    const { Cut } = await made(fixture, { Cut: 'composition' });
+    const comp = () => byId<CompositionAsset>(fixture, Cut);
+    const first = comp().tracks[0]!.id;
+    const done = await run(fixture, [
+      { command: 'add_composition_track', args: { asset: Cut, at: 0 }, as: 't' },
+      { command: 'change_composition_track', args: { asset: Cut, track: '$t', name: 'Front' } },
+      { command: 'move_composition_track', args: { asset: Cut, track: '$t', to: 5 } },
+    ]);
+    expect(done.result.isError).toBeUndefined();
+    expect(comp().tracks.map((t) => [t.id === first, t.name])).toEqual([
+      [true, 'Track 1'],
+      [false, 'Front'],
+    ]);
+    const removed = await run(fixture, [
+      { command: 'remove_composition_track', args: { asset: Cut, track: first } },
+    ]);
+    expect(removed.result.isError).toBeUndefined();
+    const last = await run(fixture, [
+      { command: 'remove_composition_track', args: { asset: Cut, track: comp().tracks[0]!.id } },
+    ]);
+    expect(last.text).toContain('keeps at least one track');
+  });
+});
diff --git a/tools/e2e/71-mcp.mjs b/tools/e2e/71-mcp.mjs
index 30fae924..901ab0ad 100644
--- a/tools/e2e/71-mcp.mjs
+++ b/tools/e2e/71-mcp.mjs
@@ -463,6 +463,59 @@ export async function mcp(t) {
       }),
     );
 
+    // 71g8. Music and compositions (#429 stage 5d): notes the agent writes, and the pattern and the
+    //       sprite laid on a composition, which comes up in its tab.
+    const composed = await callTool('run_commands', {
+      label: 'compose',
+      steps: [
+        { command: 'create_asset', args: { type: 'pattern', name: `${TOKEN_NAME} riff` }, as: 'riff' },
+        {
+          command: 'add_notes',
+          args: {
+            asset: '$riff',
+            notes: [
+              { tick: 0, length: 480, note: 'C4' },
+              { tick: 480, length: 480, note: 'E4' },
+            ],
+          },
+        },
+        { command: 'create_asset', args: { type: 'composition', name: `${TOKEN_NAME} cut` }, as: 'cut' },
+        { command: 'add_composition_track', args: { asset: '$cut', name: 'Music' }, as: 'music' },
+        {
+          command: 'add_composition_item',
+          args: { asset: '$cut', track: '$music', place: '$riff', start: 0 },
+        },
+        {
+          command: 'add_composition_item',
+          args: { asset: '$cut', track: '$music', place: heroId, start: 30 },
+        },
+      ],
+    });
+    await settle();
+    const composedMade = composed?.structuredContent?.made ?? [];
+    const riffId = composedMade.find((entry) => entry.step === 1)?.id;
+    const cutId = composedMade.find((entry) => entry.step === 3)?.id;
+    const cutView = await viewNow();
+    const riffRead = riffId ? (await callTool('get_asset', { asset: riffId }))?.structuredContent : null;
+    const cutRead = cutId ? (await callTool('get_asset', { asset: cutId }))?.structuredContent : null;
+    await callTool('undo');
+    await callTool('open', { asset: walkId });
+    await settle();
+    check(
+      'notes the agent writes read back by name, and a pattern and a sprite it lays on a composition open in its tab',
+      composed?.isError === false &&
+        cutView?.document?.asset?.id === cutId &&
+        JSON.stringify(riffRead?.notes?.map((note) => note.name)) === '["C4","E4"]' &&
+        JSON.stringify(cutRead?.items?.map((item) => [item.start, item.length])) === '[[0,480],[30,180]]' &&
+        cutRead?.objects?.length === 1,
+      JSON.stringify({
+        text: composed?.content?.[0]?.text?.slice(0, 300),
+        document: cutView?.document,
+        notes: riffRead?.notes,
+        items: cutRead?.items,
+      }),
+    );
+
     // 71h. Played by the agent, the object walks left while the user holds the arrow.
     const started = await callTool('play', { action: 'play' });
     await waitUntil('__gm.state.mode === "play"', { timeout: 10000, label: 'the game runs' });