Arpeggio material for Phrase Mode (variant 1)

- music/arpeggioGenerator.ts: diatonic triads (I-vii*) built from the
  selected key/mode via the shared degree spelling; patterns up / down /
  up-down / 1-2-3-5; one or two octaves (cycle ends on the octave; two-
  octave path continues from the turning root). Quarter-note rhythm with
  final note extended to fill the bar; title is labeled 'Arpeggio -
  <tonic> <degree> (pattern, coverage)'.
- Settings: PhraseMaterial 'arpeggio' + arpeggioDegree/Pattern/Coverage
  (defaults I / up / one-octave).
- PhraseTrainer: material option 'Arpeggios (generated)' + Chord/Pattern/
  Coverage/Meter selects; key/mode reuse the shared Target key controls.
- Tests: 9 arpeggio cases (170 total).

src/components/PhraseTrainer.tsx

@@ -19,7 +19,9 @@ import { audioEngine } from '../audio/AudioEngine';
 import { computePlayableNotes, isFrettedInstrument, positionsWithinWindow, fretWindowNotes } from '../music/playableRange';
 import { generateMelody } from '../music/melodyGenerator';
 import { generateScaleDrill } from '../music/scaleDrills';
+import { generateArpeggio, type ArpeggioDegree } from '../music/arpeggioGenerator';
 import { isMode, type ModeId } from '../music/scales';
+import { ARPEGGIO_DEGREE_LABELS } from '../music/arpeggioGenerator';
 import { scoreEvents, type Result, type Score, type ScoreEvent } from '../score/model';
 import { getNoteDetails } from '../music/NoteUtils';
 import { EXERCISES, loadExercise } from '../exercises/library';
@@ -200,6 +202,16 @@ export const PhraseTrainer = forwardRef<PhraseHandle, PhraseTrainerProps>(
                     meter: { numerator: phrase.meterNumerator, denominator: 4 },
                 }, pool);
             }
+            if (phrase.material === 'arpeggio') {
+                return generateArpeggio({
+                    keyTonic: phrase.keyTonic,
+                    keyMode: (isMode(phrase.keyMode) ? phrase.keyMode : 'major') as ModeId,
+                    degree: (phrase.arpeggioDegree as ArpeggioDegree) || 'I',
+                    pattern: phrase.arpeggioPattern,
+                    coverage: phrase.arpeggioCoverage,
+                    meter: { numerator: phrase.meterNumerator, denominator: 4 },
+                }, pool);
+            }
             if (phrase.material === 'library') {
                 const id = phrase.libraryId || EXERCISES[0]?.id;
                 if (!id) return { ok: false, error: 'No exercises available.' };
@@ -212,6 +224,7 @@ export const PhraseTrainer = forwardRef<PhraseHandle, PhraseTrainerProps>(
             return null;
         }, [phrase.material, phrase.keyTonic, phrase.keyMode, phrase.bars, phrase.meterNumerator,
             phrase.rhythmLevel, phrase.scaleDirection, phrase.scaleCoverage, phrase.libraryId,
+            phrase.arpeggioDegree, phrase.arpeggioPattern, phrase.arpeggioCoverage,
             melodySeed, pool, importedScore]);
 
         const fullScore: Result<Score> | null = useMemo(() => {
@@ -546,12 +559,13 @@ export const PhraseTrainer = forwardRef<PhraseHandle, PhraseTrainerProps>(
                                 <select value={phrase.material} onChange={e => setPhrase({ material: e.target.value as PhraseSettings['material'] })}>
                                     <option value="melody">Melodies (generated)</option>
                                     <option value="scale">Scale drills</option>
+                                    <option value="arpeggio">Arpeggios (generated)</option>
                                     <option value="library">Exercises</option>
                                     <option value="import">Imported file</option>
                                 </select>
                             </label>
 
-                            {(phrase.material === 'melody' || phrase.material === 'scale') && (
+                            {(phrase.material === 'melody' || phrase.material === 'scale' || phrase.material === 'arpeggio') && (
                                 <span style={{ fontSize: '11px', opacity: 0.7, alignSelf: 'center' }}>
                                     Key/mode: use the "Target key" controls below the sheet — shared across modes.
                                 </span>
@@ -605,6 +619,38 @@ export const PhraseTrainer = forwardRef<PhraseHandle, PhraseTrainerProps>(
                                 </>
                             )}
 
+                            {phrase.material === 'arpeggio' && (
+                                <>
+                                    <label>Chord
+                                        <select value={phrase.arpeggioDegree} onChange={e => setPhrase({ arpeggioDegree: e.target.value })}>
+                                            {(Object.keys(ARPEGGIO_DEGREE_LABELS) as ArpeggioDegree[]).map(d => (
+                                                <option key={d} value={d}>{ARPEGGIO_DEGREE_LABELS[d]}</option>
+                                            ))}
+                                        </select>
+                                    </label>
+                                    <label>Pattern
+                                        <select value={phrase.arpeggioPattern} onChange={e => setPhrase({ arpeggioPattern: e.target.value as PhraseSettings['arpeggioPattern'] })}>
+                                            <option value="up">Up</option>
+                                            <option value="down">Down</option>
+                                            <option value="updown">Up &amp; down</option>
+                                            <option value="1235">1-2-3-5</option>
+                                        </select>
+                                    </label>
+                                    <label>Coverage
+                                        <select value={phrase.arpeggioCoverage} onChange={e => setPhrase({ arpeggioCoverage: e.target.value as PhraseSettings['arpeggioCoverage'] })}>
+                                            <option value="one-octave">One octave</option>
+                                            <option value="two-octave">Two octaves</option>
+                                        </select>
+                                    </label>
+                                    <label>Meter
+                                        <select value={phrase.meterNumerator} onChange={e => setPhrase({ meterNumerator: Number(e.target.value) === 3 ? 3 : 4 })}>
+                                            <option value={4}>4/4</option>
+                                            <option value={3}>3/4</option>
+                                        </select>
+                                    </label>
+                                </>
+                            )}
+
                             {phrase.material === 'library' && (
                                 <label>Exercise
                                     <select value={phrase.libraryId || EXERCISES[0].id} onChange={e => setPhrase({ libraryId: e.target.value, startBar: 1 })}>

src/music/arpeggioGenerator.test.ts

@@ -0,0 +1,91 @@
+import { describe, it, expect } from 'vitest';
+import { generateArpeggio } from './arpeggioGenerator';
+import { scoreEvents, validateScore } from '../score/model';
+
+const strings = [40, 45, 50, 55, 59, 64];
+const pool: number[] = [];
+for (const open of strings) for (let f = 0; f <= 12; f++) pool.push(open + f);
+
+const base = {
+    keyTonic: 'C',
+    keyMode: 'major' as const,
+    meter: { numerator: 4 as const, denominator: 4 as const },
+};
+
+describe('generateArpeggio', () => {
+    it('builds a C major arpeggio (up, one octave) from the pool', () => {
+        const r = generateArpeggio({ ...base, degree: 'I', pattern: 'up', coverage: 'one-octave' }, pool);
+        expect(r.ok).toBe(true);
+        if (!r.ok) return;
+        const ev = scoreEvents(r.value);
+        // C-E-G-C: 4 notes, quarter each (plus final extension)
+        const midis = ev.map(e => e.pitch!.midi);
+        expect(midis).toEqual([48, 52, 55, 60]);
+        expect(validateScore(r.value)).toEqual([]);
+        expect(r.value.title).toContain('Arpeggio');
+        expect(r.value.title).toContain('C I');
+    });
+
+    it('down pattern reverses the ascending cycle', () => {
+        const r = generateArpeggio({ ...base, degree: 'I', pattern: 'down', coverage: 'one-octave' }, pool);
+        expect(r.ok).toBe(true);
+        if (!r.ok) return;
+        const midis = scoreEvents(r.value).map(e => e.pitch!.midi);
+        expect(midis).toEqual([60, 55, 52, 48]);
+    });
+
+    it('updown returns to the starting root without duplicating the top', () => {
+        const r = generateArpeggio({ ...base, degree: 'I', pattern: 'updown', coverage: 'one-octave' }, pool);
+        expect(r.ok).toBe(true);
+        if (!r.ok) return;
+        const midis = scoreEvents(r.value).map(e => e.pitch!.midi);
+        // ascend C-E-G-C then descend back to C; only one C5 (turning point)
+        expect(midis).toEqual([48, 52, 55, 60, 55, 52, 48]);
+        expect(midis.filter(m => m === 60)).toHaveLength(1);
+    });
+
+    it('1235 pattern ends on the octave of the root', () => {
+        const r = generateArpeggio({ ...base, degree: 'I', pattern: '1235', coverage: 'one-octave' }, pool);
+        expect(r.ok).toBe(true);
+        if (!r.ok) return;
+        const midis = scoreEvents(r.value).map(e => e.pitch!.midi);
+        expect(midis).toEqual([48, 52, 55, 60]);
+    });
+
+    it('two-octave coverage spans 12 semitones beyond the first cycle', () => {
+        const r = generateArpeggio({ ...base, degree: 'I', pattern: 'up', coverage: 'two-octave' }, pool);
+        expect(r.ok).toBe(true);
+        if (!r.ok) return;
+        const midis = scoreEvents(r.value).map(e => e.pitch!.midi);
+        expect(midis).toEqual([48, 52, 55, 60, 64, 67, 72]);
+    });
+    it('spells the dominant triad G-B-D in C major', () => {
+        const r = generateArpeggio({ ...base, degree: 'V', pattern: 'up', coverage: 'one-octave' }, pool);
+        expect(r.ok).toBe(true);
+        if (!r.ok) return;
+        const pcs = scoreEvents(r.value).map(e => e.pitch!.midi % 12);
+        expect(pcs).toEqual([7, 11, 2, 7]); // G B D G
+    });
+
+    it('spells the leading-tone dim triad B-D-F in C major', () => {
+        const r = generateArpeggio({ ...base, degree: 'vii0', pattern: 'up', coverage: 'one-octave' }, pool);
+        expect(r.ok).toBe(true);
+        if (!r.ok) return;
+        const pcs = scoreEvents(r.value).map(e => e.pitch!.midi % 12);
+        expect(pcs).toEqual([11, 2, 5, 11]); // B D F B
+    });
+
+    it('fails cleanly when the pool cannot fit a full triad cycle', () => {
+        // Only frets 0-1 on all strings: no complete C-E-G cycle with octave
+        const tiny: number[] = [];
+        for (const open of strings) for (let f = 0; f <= 1; f++) tiny.push(open + f);
+        const r = generateArpeggio({ ...base, degree: 'I', pattern: 'up', coverage: 'one-octave' }, tiny);
+        expect(r.ok).toBe(false);
+    });
+
+    it('is deterministic for identical configs', () => {
+        const a = generateArpeggio({ ...base, degree: 'IV', pattern: 'updown', coverage: 'one-octave' }, pool);
+        const b = generateArpeggio({ ...base, degree: 'IV', pattern: 'updown', coverage: 'one-octave' }, pool);
+        expect(a).toEqual(b);
+    });
+});

src/music/arpeggioGenerator.ts

@@ -0,0 +1,181 @@
+/**
+ * Arpeggio generator (Phrase Mode material).
+ *
+ * Diatonic triads (I, ii, iii, IV, V, vi, vii°) built from the selected
+ * key/mode; each practice run arpeggiates ONE chord — the user picks the
+ * degree, the pattern (up / down / up-down / 1-2-3-5) and the coverage
+ * (one or two octaves). Chord tones are spelled via the key's degree
+ * spelling (same machinery as melody/scale generators), so spelling and
+ * validation match the Phrase Mode invariants exactly.
+ */
+import { PPQ, validateScore, type Result, type Score, type ScoreEvent } from '../score/model';
+import { keyFor, type KeyContext, type ModeId } from './scales';
+import { STEP_LETTERS, LETTER_PC, type StepLetter } from '../score/model';
+
+export type ArpeggioDegree = 'I' | 'ii' | 'iii' | 'IV' | 'V' | 'vi' | 'vii0';
+export type ArpeggioPattern = 'up' | 'down' | 'updown' | '1235';
+export type ArpeggioCoverage = 'one-octave' | 'two-octave';
+
+export interface ArpeggioConfig {
+    readonly keyTonic: string;
+    readonly keyMode: ModeId;
+    readonly degree: ArpeggioDegree;
+    readonly pattern: ArpeggioPattern;
+    readonly coverage: ArpeggioCoverage;
+    readonly meter: { readonly numerator: 3 | 4; readonly denominator: 4 };
+}
+
+/** Degree index (0-based) into the scale for each arpeggio degree label. */
+const DEGREE_INDEX: Record<ArpeggioDegree, number> = {
+    I: 0, ii: 1, iii: 2, IV: 3, V: 4, vi: 5, 'vii0': 6,
+};
+
+export const ARPEGGIO_DEGREE_LABELS: Record<ArpeggioDegree, string> = {
+    I: 'I', ii: 'ii', iii: 'iii', IV: 'IV', V: 'V', vi: 'vi', 'vii0': 'vii°',
+};
+
+/** pc of a spelled degree (step letter + alter). */
+const degreePc = (d: { step: StepLetter; alter: number }): number =>
+    (LETTER_PC[STEP_LETTERS.indexOf(d.step)] + d.alter + 144) % 12;
+
+/**
+ * Chord-tone midi notes of the diatonic triad on `degreeIndex` (0-based),
+ * intersected with the playable pool, ascending.
+ */
+function chordTonesInPool(key: KeyContext, degreeIndex: number, pool: number[]): number[] {
+    const steps = [0, 2, 4].map(offset => (degreeIndex + offset) % 7);
+    const pcs = new Set(steps.map(i => degreePc(key.degrees[i])));
+    return pool.filter(midi => pcs.has(((midi % 12) + 12) % 12));
+}
+
+/** Spelling (step, alter) for a midi note in the key — via scale degrees. */
+function spellInKey(key: KeyContext, midi: number): { step: StepLetter; alter: number; octave: number } | null {
+    const pc = ((midi % 12) + 12) % 12;
+    const d = key.degrees.find(deg => degreePc(deg) === pc);
+    if (!d) return null;
+    const octave = (midi - pc) / 12 - 1;
+    return { step: d.step, alter: d.alter, octave };
+}
+
+/**
+ * Build the arpeggio path: chord tones ascending from the lowest available
+ * root (degree tone) that allows a full one/two-octave cycle in the pool.
+ * Pattern up/down/updown/1235 is applied to one octave cycle.
+ */
+function buildPath(key: KeyContext, degreeIndex: number, pool: number[], coverage: ArpeggioCoverage, pattern: ArpeggioPattern): number[] | null {
+    const tones = chordTonesInPool(key, degreeIndex, pool);
+    if (tones.length < 3) return null; // need at least one full triad
+
+    const rootPc = degreePc(key.degrees[degreeIndex]);
+    const octaveCycle = (startMidi: number): number[] => {
+        // chord tones >= startMidi within one octave, INCLUDING the octave
+        // of the root (an arpeggio cycle conventionally ends on the octave)
+        const cycle: number[] = [];
+        for (const midi of tones) {
+            if (midi >= startMidi && midi <= startMidi + 12) cycle.push(midi);
+        }
+        if (!cycle.includes(startMidi + 12) && pool.includes(startMidi + 12)) {
+            cycle.push(startMidi + 12);
+        }
+        return cycle.sort((a, b) => a - b);
+    };
+
+    const cycles: number[][] = [];
+    // candidate roots: chord-tone midis with pc == rootPc, ascending
+    const roots = tones.filter(m => ((m % 12) + 12) % 12 === rootPc);
+    const octavesWanted = coverage === 'one-octave' ? 1 : 2;
+    for (const root of roots) {
+        const first = octaveCycle(root);
+        if (first.length < 3 || first[0] !== root) continue;
+        // second octave: tones one octave above `root`
+        const second = first.map(m => m + 12).filter(m => pool.includes(m));
+        if (octavesWanted === 2 && second.length < 4) continue;
+        cycles.push(first);
+        break; // lowest fitting root
+    }
+    if (cycles.length === 0) return null;
+
+    const base = cycles[0];
+    const up = octavesWanted === 2
+        // base already ends on the octave of the root — the second octave
+        // continues from there (drop the duplicated turning root)
+        ? [...base, ...base.map(m => m + 12).slice(1)]
+        : base;
+
+    switch (pattern) {
+        case 'up': return up;
+        case 'down': return [...up].reverse();
+        case 'updown': {
+            // ascend then descend, dropping the duplicated turning note
+            const desc = [...up].reverse().slice(1);
+            return [...up, ...desc];
+        }
+        case '1235': {
+            // root, third, fifth, octave (of the root) — repeated per octave
+            const path: number[] = [];
+            for (let oct = 0; oct < octavesWanted; oct++) {
+                path.push(base[0] + 12 * oct);
+                path.push(base[1] + 12 * oct);
+                path.push(base[2] + 12 * oct);
+                path.push(base[0] + 12 * (oct + 1));
+            }
+            return path;
+        }
+    }
+}
+
+export function generateArpeggio(
+    config: ArpeggioConfig,
+    eligiblePitches: number[],
+): Result<Score> {
+    const key = keyFor(config.keyTonic, config.keyMode);
+    const pool = Array.from(new Set(eligiblePitches.filter(m => Number.isInteger(m)))).sort((a, b) => a - b);
+    if (pool.length === 0) return { ok: false, error: 'No playable notes in the selected range — widen the note set.' };
+
+    const degreeIndex = DEGREE_INDEX[config.degree];
+    const path = buildPath(key, degreeIndex, pool, config.coverage, config.pattern);
+    if (!path || path.length === 0) {
+        return {
+            ok: false,
+            error: 'The complete arpeggio does not fit the playable range — widen the range (strings/fret window) or pick another degree.',
+        };
+    }
+
+    // ---- Quarter-note rhythm, final note extended to fill its bar ---------
+    const full = config.meter.numerator * PPQ;
+    if (path.length * PPQ > 8 * full) {
+        return { ok: false, error: 'This arpeggio is longer than 8 bars — reduce the coverage.' };
+    }
+    const barCount = Math.max(1, Math.ceil((path.length * PPQ) / full));
+    const totalTicks = barCount * full;
+    const lastDuration = PPQ + (totalTicks - path.length * PPQ);
+
+    const events: ScoreEvent[] = [];
+    let cursor = 0;
+    for (let i = 0; i < path.length; i++) {
+        const dur = i === path.length - 1 ? lastDuration : PPQ;
+        const spelled = spellInKey(key, path[i]);
+        if (!spelled) return { ok: false, error: 'Internal error spelling arpeggio pitch.' };
+        events.push({ id: `a${i}`, startTick: cursor, durationTicks: dur, pitch: { midi: path[i], ...spelled } });
+        cursor += dur;
+    }
+
+    const chordName = `${key.tonic} ${ARPEGGIO_DEGREE_LABELS[config.degree]}`;
+    const patternLabel = { up: 'up', down: 'down', updown: 'up & down', '1235': '1-2-3-5' }[config.pattern];
+    const score: Score = {
+        version: 1,
+        id: `arpeggio-${config.keyTonic}-${config.keyMode}-${config.degree}-${config.pattern}-${config.coverage}-${config.meter.numerator}4`,
+        title: `Arpeggio — ${chordName} (${patternLabel}, ${config.coverage})`,
+        meter: config.meter,
+        key: { tonic: config.keyTonic, mode: config.keyMode, signature: key.signature },
+        measures: Array.from({ length: barCount }, (_, i) => ({
+            number: i + 1,
+            startTick: i * full,
+            durationTicks: full,
+        })),
+        voices: [{ id: 'melody', events }],
+    };
+    const problems = validateScore(score);
+    if (problems.length > 0) return { ok: false, error: `Internal arpeggio error: ${problems[0]}` };
+    return { ok: true, value: score };
+}

src/types/SettingsTypes.ts

@@ -39,7 +39,7 @@ export interface RhythmSettings {
     volume: number;
 }
 
-export type PhraseMaterial = 'melody' | 'scale' | 'library' | 'import';
+export type PhraseMaterial = 'melody' | 'scale' | 'arpeggio' | 'library' | 'import';
 export type PhrasePace = 'step' | 'tempo';
 
 export interface PhraseSettings {
@@ -53,6 +53,10 @@ export interface PhraseSettings {
     rhythmLevel: 1 | 2 | 3;
     scaleCoverage: 'one-octave' | 'two-octave' | 'position';
     scaleDirection: 'up' | 'down' | 'updown';
+    /** Arpeggio settings (material = 'arpeggio'). */
+    arpeggioDegree: string; // ArpeggioDegree
+    arpeggioPattern: 'up' | 'down' | 'updown' | '1235';
+    arpeggioCoverage: 'one-octave' | 'two-octave';
     /** Phrase-local fret window (guitar/bass) — overrides the note set. */
     fretWindowEnabled: boolean;
     fretMin: number;
@@ -79,6 +83,9 @@ export const DEFAULT_PHRASE_SETTINGS: PhraseSettings = {
     rhythmLevel: 1,
     scaleCoverage: 'one-octave',
     scaleDirection: 'updown',
+    arpeggioDegree: 'I',
+    arpeggioPattern: 'up',
+    arpeggioCoverage: 'one-octave',
     fretWindowEnabled: false,
     fretMin: 0,
     fretMax: 4,