ai-agent/reel/music/harmony.ts

/**
 * The harmony and the tunes, as data.
 *
 * Key: D major. The loop is 王道進行, the J-pop "royal road" — IV△7 – V7 –
 * iii7 – vi (G△7 – A7 – F#m7 – Bm7), one chord per bar — a nod to Tokunia's
 * Japanese name. The night breakdown sits on Bm and G△7, the build climbs
 * Em7 – F#m7 – G△7 – A9sus4 → A, and the film ends on a held D(add9).
 *
 * The HOOK is built from E-F#-A-B-C# — the 陽音階 (yo scale) on E — so it
 * sits on every chord of the loop: the same two bars over G–A and F#m–Bm.
 */

export type ChordName = "G" | "A" | "F#m" | "Bm" | "Em" | "Asus" | "D";

/** MIDI notes per chord: the sub root, the chord voicing (pads + stabs), the arp's five tones. */
export const VOICING: Record<ChordName, { root: number; chord: number[]; arp: number[] }> = {
  G: { root: 31, chord: [55, 59, 62, 66, 69], arp: [67, 71, 74, 78, 81] }, // G△9
  A: { root: 33, chord: [57, 61, 64, 67, 71], arp: [69, 73, 76, 79, 83] }, // A9
  "F#m": { root: 30, chord: [54, 57, 61, 64, 69], arp: [66, 69, 73, 76, 78] }, // F#m7
  Bm: { root: 35, chord: [54, 59, 62, 66, 69], arp: [66, 71, 74, 78, 81] }, // Bm7
  Em: { root: 28, chord: [52, 55, 59, 62, 66], arp: [64, 67, 71, 74, 78] }, // Em9
  Asus: { root: 33, chord: [57, 62, 64, 67, 71], arp: [69, 74, 76, 79, 81] }, // A9sus4
  D: { root: 38, chord: [50, 57, 62, 64, 66, 69], arp: [74, 76, 78, 81, 86] }, // D(add9)
};

/** The night's open, low voicings (bars 31–34). */
export const NIGHT_VOICING: Partial<Record<ChordName, number[]>> = {
  Bm: [47, 54, 62, 69, 73], // Bm9: B2 F#3 D4 A4 C#5
  G: [43, 50, 59, 66, 69], // G△9: G2 D3 B3 F#4 A4
};

const LOOP: ChordName[] = ["G", "A", "F#m", "Bm"];

/** Where the royal-road loop (re)starts on G. */
const LOOP_STARTS = [1, 5, 39, 45, 51, 59];

/** The chord sounding at `bar`, `beat` (1-indexed). */
export function chordAt(bar: number, beat = 1): ChordName {
  if (bar >= 63) return "D";
  if (bar >= 31 && bar <= 32) return "Bm";
  if (bar >= 33 && bar <= 34) return "G";
  if (bar === 35) return "Em";
  if (bar === 36) return "F#m";
  if (bar === 37) return "G";
  if (bar === 38) return beat < 3 ? "Asus" : "A";
  // the last bar of drop 3 leans on the dominant for the final cadence
  if (bar === 62 && beat >= 3) return "Asus";
  const start = Math.max(...LOOP_STARTS.filter((s) => s <= bar));
  return LOOP[(bar - start) % 4];
}

/** A melody note: start and length in 16ths from the phrase's downbeat, MIDI pitch. */
export type Note = [start: number, len: number, midi: number];

const F5 = 78; // F#5
const A5 = 81;
const B5 = 83;
const E5 = 76;
const D5 = 74;
const CS5 = 73; // C#5

/** Bar 1 of the hook — the 3+3+2 / 3+3+2 call over IV△7 (or iii7). */
const HOOK_CALL: Note[] = [
  [0, 3, F5],
  [3, 3, A5],
  [6, 2, F5],
  [8, 3, E5],
  [11, 3, F5],
  [14, 2, A5],
];

/** THE HOOK — two bars, the film's theme: call, then the answer falling to E. */
export const HOOK: Note[] = [...HOOK_CALL, [16, 3, B5], [19, 3, A5], [22, 2, F5], [24, 6, E5]];

/** The hook's second statement in a 4-bar phrase: same call, the answer resolves to D. */
export const HOOK_ANSWER: Note[] = [
  ...HOOK_CALL,
  [16, 3, B5],
  [19, 3, A5],
  [22, 2, F5],
  [24, 2, E5],
  [26, 2, F5],
  [28, 4, D5],
];

/**
 * The counter-line (4 bars over G–A–F#m–Bm): the hook in augmentation — its
 * notes at half speed — so the chapters between the drops still hum the theme.
 */
export const COUNTER: Note[] = [
  [0, 6, F5],
  [6, 6, A5],
  [12, 4, F5],
  [16, 6, E5],
  [22, 6, F5],
  [28, 4, A5],
  [32, 6, B5], // a 4–3 suspension over F#m7…
  [38, 6, A5], // …resolving
  [44, 4, F5],
  [48, 8, D5],
  [56, 4, CS5],
  [60, 4, E5],
];

/** The arp: 16 steps into the chord's five arp tones — 3+3+3+3+4, syncopated against the kick. */
export const ARP_STEPS = [0, 2, 4, 1, 3, 4, 0, 2, 4, 1, 3, 4, 0, 2, 3, 4];
/** Accents on each group's first note. */
export const ARP_VEL = [1, 0.62, 0.7, 0.92, 0.62, 0.7, 0.95, 0.62, 0.7, 0.92, 0.62, 0.7, 0.95, 0.62, 0.7, 0.66];

/** Mid-bass rhythms: [16th position, length in 16ths, octave offset in semitones]. */
export const BASS_RHYTHM = {
  /** classic house offbeats with an octave pickup */
  offbeat: [
    [2, 2, 0],
    [6, 2, 0],
    [10, 2, 0],
    [14, 1, 0],
    [15, 1, 12],
  ],
  /** galloping offbeats — the drive chapters and the drops */
  gallop: [
    [2, 1, 0],
    [3, 1, 0],
    [6, 1, 0],
    [7, 1, 12],
    [10, 1, 0],
    [11, 1, 0],
    [14, 1, 0],
    [15, 1, 12],
  ],
  /** octave bounce under the notifications */
  bounce: [
    [2, 2, 0],
    [6, 2, 12],
    [10, 2, 0],
    [14, 2, 12],
  ],
  /** straight eighths for the last two bars of the build */
  build: [
    [0, 2, 0],
    [2, 2, 0],
    [4, 2, 0],
    [6, 2, 0],
    [8, 2, 0],
    [10, 2, 0],
    [12, 2, 0],
    [14, 2, 12],
  ],
} satisfies Record<string, [number, number, number][]>;

/** Chord-stab rhythms (16th positions). */
export const STAB_RHYTHM = {
  /** the drops: 3+3+4+3+3, locked to the hook's syncopation */
  drop: [0, 3, 6, 10, 13],
  /** the grooves: on the offbeats, between the kicks */
  offbeat: [2, 6, 10, 14],
};

/**
 * The notification bells, one per score PINGS entry (same order). A second
 * pitch is a grace note a 16th later: the "ask" rises, the "answer" settles.
 * The cascade climbs the scale to C#7, the dominant's third, into the dropout.
 */
export const PING_NOTES: (number | [number, number])[] = [
  81, // 25.1 A5
  86, // 25.3 D6
  85, // 26.1 C#6
  88, // 26.3 E6
  [83, 88], // 27.1 the ask: B5 → E6
  [90, 86], // 28.1 the answer: F#6 → D6
  78, // 29.1 cascade: F#5
  81, // 29.2 A5
  83, // 29.3 B5
  86, // 29.4 D6
  88, // 30.1 E6
  90, // 30.1+ F#6
  93, // 30.2 A6
  95, // 30.2+ B6
  97, // 30.3 C#7
];

/** The cron chimes (CHIMES, same order): the hook's first four notes, slowed to a crawl. */
export const CHIME_NOTES = [90, 93, 90, 88]; // F#6 A6 F#6 E6