Drift

import {chord, defineCue, gain, lowPass, mix, noise, normalize, note, pad, sequence, sine, type CueDefinition} from "odori";

export type BedDriftOptions = {
  /** Root of the home chord, as a note name. */
  root?: string;
  /** Peak level before the mix normalizes the whole track. */
  peak?: number;
};

/**
 * Sixteen seconds of slow breathing: the home chord swells and lets go, and a
 * warmer chord answers it, overlapping so the seam between them is a change of
 * colour rather than an event. Nothing in it marks time — no pulse, no beat —
 * which is the bed for a cut that narration is already pacing.
 *
 * Everything sits below the voice: the pads are low passed under a kilohertz,
 * the drone is an octave under the root, and the air is closer to room tone
 * than to texture.
 */
export const bedDrift = ({root = "a2", peak = 0.5}: BedDriftOptions = {}): CueDefinition => {
  // One breath is four seconds. Two breaths each way is the phrase.
  const breath = 4 * 48000;
  const samples = breath * 4;

  // The answering chord, a major third below: the relative major seventh,
  // which agrees with the home chord about every note but one.
  const answer = note(root) * 2 ** (-4 / 12);

  return defineCue({
    name: "bed.drift",
    durationInFrames: Math.round((samples / 48000) * 30),
    loops: true,
    params: {root, peak},
    render: () =>
      normalize(
        mix(
          // The two swells, placed so one rises while the other releases.
          sequence(
            [
              {
                at: 0,
                length: 2.5,
                play: (length: number) =>
                  lowPass(pad(chord(root, "minor7"), length, {envelope: {attack: 3.5, sustain: 1, release: 4}}), 850),
                gain: 0.85,
              },
              {
                at: 1.5,
                length: 2.5,
                play: (length: number) =>
                  lowPass(pad(chord(answer, "major7"), length, {envelope: {attack: 3.5, sustain: 1, release: 4}}), 850),
                gain: 0.7,
              },
            ],
            {bpm: 60, division: 1, samples},
          ),
          // A drone an octave down holds through both, which is what makes the
          // chord change read as weather rather than as a cut.
          gain(sine(samples, note(root) / 2), 0.16),
          // Room tone. Just enough that silence between swells is not digital.
          gain(lowPass(noise(samples, 7), 350), 0.05),
        ),
        peak,
      ),
  });
};

import {CueWave, defineComponentPreview} from "odori/preview";
import {bedDrift, type BedDriftOptions} from "./bed-drift";

const Wave = ({root, peak}: BedDriftOptions) => <CueWave cue={bedDrift({root, peak})} />;

export default defineComponentPreview({
  title: "Drift",
  category: "Sound/Beds",
  description: "Soft ambient pad for narration.",
  component: Wave,
  canvas: {width: 1920, height: 1080, duration: "5s"},
  controls: {
    root: {type: "select", defaultValue: "a2", options: ["f2", "g2", "a2", "c3"]},
    peak: {type: "number", defaultValue: 0.5, min: 0.1, max: 1, step: 0.05},
  },
  examples: [{name: "Default", props: {}}, {name: "Lower", props: {root: "f2"}}],
});

import {Scene, Video} from "odori";
import {BedDrift} from "../components/bed-drift/bed-drift";

<Video>
  <Scene id="bed-drift" duration="16s">
    <BedDrift />
  </Scene>
</Video>