Pick a pattern's sign in one row, as a song's (#364)

A pattern had two rows for its meter, Beats per bar and Beat, while a
song has had one row Sign since #363. Both now pick from the same list.

- The list of signs and how a sign becomes a meter moved to time.ts.
  Song and pattern share it.
- A pattern keeps its meter in `sign`. The fields `beats` and `beat`
  are gone, a sign that is not in the list counts as 4/4.
- Create pattern in a song hands the song's sign to the new pattern.
- The four patterns of cbbf160bb7e8 were moved to `sign` by hand
  (three 4/4, one 3/4). The other projects only had 4/4, which stays
  the default.

Tests:
- Unit pattern/embedded: 30 green (1 new, 2 rewritten), the
  counter-test reading `beats` again turns 2 red
- e2e 64 + 65 (melektaus-atx): ALL PASSED, 85 checks
- Gate (melektaus-atx): CHECK EXIT 0, 272 files, 4215 tests

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

src/core/music/embedded.ts

@@ -15,8 +15,9 @@ import { findAsset, findAssetOf, type Project } from '../model/Project';
 import { assetNamedBy, renewClipIds } from '../model/sound';
 import { ASSET_FX_KEY, assetFxOf, NO_FX } from '../properties/assetFx';
 import { nextNumberedName } from '../commands/naming';
-import { PATTERN_BEAT_KEY, PATTERN_BEATS_KEY, PATTERN_TEMPO_KEY, patternInstrument } from './pattern';
+import { PATTERN_SIGN_KEY, PATTERN_TEMPO_KEY, patternInstrument } from './pattern';
 import { type SongItem, songMeter, songTempo, type SongTrack } from './song';
+import { signOf } from './time';
 
 export const EMBEDDABLE_TYPES: readonly AssetType[] = ['sound', 'pattern', 'soundfx'];
 
@@ -71,12 +72,7 @@ export function assetTitle(project: Project, asset: Asset): string {
 
 /** The tempo and the meter of a song, as the props a pattern made in it starts with. */
 export function songClockProps(props: PropertyBag): PropertyBag {
-  const meter = songMeter(props);
-  return {
-    [PATTERN_TEMPO_KEY]: songTempo(props),
-    [PATTERN_BEATS_KEY]: meter.beats,
-    [PATTERN_BEAT_KEY]: String(meter.unit),
-  };
+  return { [PATTERN_TEMPO_KEY]: songTempo(props), [PATTERN_SIGN_KEY]: signOf(songMeter(props)) };
 }
 
 /**

src/core/music/pattern.ts

@@ -8,7 +8,7 @@ import { HIGHEST_NOTE, LOWEST_NOTE } from '../instrument/notes';
 import type { PatternAsset } from '../model/Asset';
 import { type PropertyBag, textOf } from '../model/Properties';
 import { heldLoop, type LoopRange, type Sequence } from './sequence';
-import { heldMeter, heldTempo, type Meter, ticksPerBar } from './time';
+import { DEFAULT_SIGN, heldTempo, type Meter, signMeter, ticksPerBar } from './time';
 
 export interface PatternNote {
   id: string;
@@ -24,8 +24,7 @@ export interface PatternNote {
 export const PATTERN_INSTRUMENT_KEY = 'instrument';
 export const PATTERN_BARS_KEY = 'bars';
 export const PATTERN_GRID_KEY = 'grid';
-export const PATTERN_BEATS_KEY = 'beats';
-export const PATTERN_BEAT_KEY = 'beat';
+export const PATTERN_SIGN_KEY = 'sign';
 export const PATTERN_TEMPO_KEY = 'tempo';
 
 export const DEFAULT_BARS = 4;
@@ -49,7 +48,6 @@ const GRIDS: readonly (readonly [string, number])[] = [
 ];
 
 export const GRID_OPTIONS = GRIDS.map(([value]) => ({ value, label: value }));
-export const BEAT_OPTIONS = [1, 2, 4, 8, 16, 32].map((unit) => ({ value: String(unit), label: `1/${unit}` }));
 
 export function gridTicks(grid: string): number {
   return (GRIDS.find(([value]) => value === grid) ?? GRIDS[4]!)[1];
@@ -66,10 +64,7 @@ function wholeNumber(
 }
 
 export function patternMeter(props: PropertyBag): Meter {
-  return heldMeter({
-    beats: wholeNumber(props[PATTERN_BEATS_KEY], 4, 1, 32),
-    unit: Number(textOf(props[PATTERN_BEAT_KEY] ?? '4')),
-  });
+  return signMeter(textOf(props[PATTERN_SIGN_KEY] ?? DEFAULT_SIGN));
 }
 
 export function patternTempo(props: PropertyBag): number {

src/core/music/song.ts

@@ -14,7 +14,7 @@ import { findSound } from '../model/sound';
 import { pickedFx } from '../properties/assetFx';
 import { gridTicks, GRID_OPTIONS, patternInstrument, patternLength } from './pattern';
 import { heldLoop, type LoopRange, type Sequence, type SequenceClip, type SequenceNote } from './sequence';
-import { heldMeter, heldTempo, type Meter, secondsOfTicks, ticksPerBar } from './time';
+import { DEFAULT_SIGN, heldTempo, type Meter, secondsOfTicks, signMeter, ticksPerBar } from './time';
 
 export interface SongTrack {
   id: string;
@@ -59,26 +59,6 @@ export const SONG_TEMPO_KEY = 'tempo';
 export const SONG_SIGN_KEY = 'sign';
 export const SONG_GRID_KEY = 'grid';
 
-/** The time signatures a song is written in (#363), one row for both numbers. */
-export const SIGNS: readonly string[] = [
-  '1/2',
-  '2/2',
-  '3/2',
-  '1/4',
-  '2/4',
-  '3/4',
-  '4/4',
-  '5/4',
-  '6/4',
-  '5/8',
-  '6/8',
-  '7/8',
-  '8/8',
-  '9/8',
-];
-export const DEFAULT_SIGN = '4/4';
-export const SIGN_OPTIONS = SIGNS.map((sign) => ({ value: sign, label: sign }));
-
 export const DEFAULT_SONG_GRID = 'bar';
 export const SONG_GRID_OPTIONS = [{ value: 'bar', label: 'Bar' }, ...GRID_OPTIONS];
 /** A new song has this many tracks. */
@@ -97,11 +77,8 @@ export function itemMaxDb(kind: SongItemKind): number {
   return kind === 'sound' ? SOUND_ITEM_MAX_DB : 0;
 }
 
-/** The meter of a song's sign; 4/4 where it is not one of `SIGNS`. */
 export function songMeter(props: PropertyBag): Meter {
-  const sign = textOf(props[SONG_SIGN_KEY] ?? DEFAULT_SIGN);
-  const [beats, unit] = (SIGNS.includes(sign) ? sign : DEFAULT_SIGN).split('/');
-  return heldMeter({ beats: Number(beats), unit: Number(unit) });
+  return signMeter(textOf(props[SONG_SIGN_KEY] ?? DEFAULT_SIGN));
 }
 
 export function songTempo(props: PropertyBag): number {

src/core/music/time.ts

@@ -28,6 +28,36 @@ export function heldMeter(meter: Meter): Meter {
   return { beats, unit };
 }
 
+/** The time signatures a song or a pattern is written in (#363, #364), one row for both numbers. */
+export const SIGNS: readonly string[] = [
+  '1/2',
+  '2/2',
+  '3/2',
+  '1/4',
+  '2/4',
+  '3/4',
+  '4/4',
+  '5/4',
+  '6/4',
+  '5/8',
+  '6/8',
+  '7/8',
+  '8/8',
+  '9/8',
+];
+export const DEFAULT_SIGN = '4/4';
+export const SIGN_OPTIONS = SIGNS.map((sign) => ({ value: sign, label: sign }));
+
+/** The meter of a sign; 4/4 where it is not one of `SIGNS`. */
+export function signMeter(sign: string): Meter {
+  const [beats, unit] = (SIGNS.includes(sign) ? sign : DEFAULT_SIGN).split('/');
+  return heldMeter({ beats: Number(beats), unit: Number(unit) });
+}
+
+export function signOf(meter: Meter): string {
+  return `${meter.beats}/${meter.unit}`;
+}
+
 /** A tempo between `MIN_TEMPO` and `MAX_TEMPO`; 0 and anything that is not a number is the default. */
 export function heldTempo(tempo: number): number {
   if (!Number.isFinite(tempo) || tempo <= 0) return DEFAULT_TEMPO;

src/core/properties/PropertySchema.ts

@@ -105,28 +105,24 @@ import { SHADER_KEY, shaderOf, shaderParamDefs } from './shaders';
 import { SHADER_RESOLUTION_KEY, SHADER_RESOLUTION_OPTIONS } from './cameraShader';
 import { LOOP_KEY as SOUND_LOOP_KEY, VOLUME_KEY as SOUND_VOLUME_KEY } from './sounds';
 import {
-  BEAT_OPTIONS,
   DEFAULT_BARS,
   DEFAULT_GRID,
   GRID_OPTIONS,
   MAX_BARS,
   PATTERN_BARS_KEY,
-  PATTERN_BEAT_KEY,
-  PATTERN_BEATS_KEY,
   PATTERN_GRID_KEY,
   PATTERN_INSTRUMENT_KEY,
+  PATTERN_SIGN_KEY,
   PATTERN_TEMPO_KEY,
 } from '../music/pattern';
 import {
-  DEFAULT_SIGN,
   DEFAULT_SONG_GRID,
-  SIGN_OPTIONS,
   SONG_GRID_KEY,
   SONG_GRID_OPTIONS,
   SONG_SIGN_KEY,
   SONG_TEMPO_KEY,
 } from '../music/song';
-import { DEFAULT_TEMPO, MAX_TEMPO, MIN_TEMPO } from '../music/time';
+import { DEFAULT_SIGN, DEFAULT_TEMPO, MAX_TEMPO, MIN_TEMPO, SIGN_OPTIONS } from '../music/time';
 import { ASSET_FX_KEY } from './assetFx';
 import { BUS_FX_KEY, BUS_INTO_KEY, BUS_KEY, BUS_VOLUME_KEY } from './buses';
 import { Theme } from '../../ui';
@@ -737,17 +733,7 @@ const ASSET_SCHEMAS: Record<AssetType, PropertySchema> = {
       decimals: 0,
     },
     { key: PATTERN_GRID_KEY, label: 'Grid', kind: 'enum', default: DEFAULT_GRID, options: GRID_OPTIONS },
-    {
-      key: PATTERN_BEATS_KEY,
-      label: 'Beats per bar',
-      kind: 'number',
-      default: 4,
-      min: 1,
-      max: 32,
-      step: 1,
-      decimals: 0,
-    },
-    { key: PATTERN_BEAT_KEY, label: 'Beat', kind: 'enum', default: '4', options: BEAT_OPTIONS },
+    { key: PATTERN_SIGN_KEY, label: 'Sign', kind: 'enum', default: DEFAULT_SIGN, options: SIGN_OPTIONS },
     {
       key: PATTERN_TEMPO_KEY,
       label: 'Tempo (BPM)',