drone.js

// Drone — tanpura, pad, shruti, harmonic, or cinematic strings; optional slow melody.
// Tanpura strings: Pa, Sa, Sa (detuned), SA (low octave).
// Run: node examples/drone.js 130.81 30s
// Run: node examples/drone.js freq=C3 -d 2m
// Run: node examples/drone.js voice=pad freq=D3 -d 1m
// Keys: space pause · ↑/↓ ±semitone · ←/→ ±5 cents · 1-7 scale degrees · q quit

import { AudioContext } from 'web-audio-api'
import { init } from './graphs/drone.js'
import { args, num, sec, keys, status, clearLine, noteName, pausedTag, help } from './utils.js'

help({
  description: 'play a sustained drone or cinematic string ensemble with optional melody',
  usage: ['', '[frequency] [duration]', 'freq=C3 dur=2m', 'voice=pad freq=D3 -d 1m'],
  options: [
    ['voice=<type>', 'tanpura (default), pad, shruti, harmonic, or strings'],
    ['melody=<mode>', 'off (default), pentatonic, or dorian'],
    ['freq=<hz|note>', 'Sa frequency or note name (default: 130.81 / C3)'],
    ['-d, --duration <time>', 'run time with optional s/m/h suffix (default: 5m)'],
  ],
  controls: [
    ['Space', 'pause/resume'], ['↑ / ↓', 'move one semitone'], ['← / →', 'move 5 cents'],
    ['1–7', 'select a major-scale degree above the current base'], ['Q / Esc', 'quit'],
  ],
})

let { pos, $ } = args()

let voice = String($('voice', 'tanpura')).toLowerCase()
let f = num(pos.find(t => /^\d/.test(t) && !/[smh]$/.test(t) || /^[A-G][#b]?\d$/i.test(t)) || $('freq', 130.81))
let dur = sec(pos.find(t => /\d[smh]$/.test(t)) || $('dur', '300'))

let ctx = new AudioContext()
await ctx.resume()

let demo = init(ctx, { frequency: f, duration: dur, voice, melody: String($('melody', 'off')).toLowerCase(), seed: Math.random() * 0xffffffff })
let master = demo.data.master
let retune = frequency => { f = frequency; demo.data.retune(frequency) }

let render = status()
let draw = () => render(`Sa = ${f.toFixed(2)}Hz  ${noteName(f).padEnd(4)}  ↑↓ semi · ←→ cents · 1-7 scale · space pause · q quit${pausedTag(ctx)}`)
let ui = setInterval(draw, 80)

let scale = [0, 2, 4, 5, 7, 9, 11] // C major semitone offsets
let base = f
let semiShift = v => retune(base * 2 ** (v / 12))

keys({
  up: () => { base = f * 2 ** (1 / 12); retune(base) },
  down: () => { base = f * 2 ** (-1 / 12); retune(base) },
  right: () => { base = f * 2 ** (5 / 1200); retune(base) },  // +5 cents
  left: () => { base = f * 2 ** (-5 / 1200); retune(base) },
  1: () => semiShift(scale[0]), 2: () => semiShift(scale[1]), 3: () => semiShift(scale[2]),
  4: () => semiShift(scale[3]), 5: () => semiShift(scale[4]), 6: () => semiShift(scale[5]),
  7: () => semiShift(scale[6]),
}, () => {
  clearInterval(ui); clearLine()
  let t = ctx.currentTime
  master.gain.cancelScheduledValues(t)
  master.gain.setValueAtTime(master.gain.value, t)
  master.gain.linearRampToValueAtTime(0, t + 0.3)
  setTimeout(() => ctx.close(), 400)
}, ctx)

console.log(`Drone: ${voice}, Sa = ${f.toFixed(2)}Hz ${noteName(f)} (${dur}s)  ↑↓ semi · ←→ cents · 1-7 scale · q quit`)

setTimeout(() => { clearInterval(ui); clearLine(); ctx.close(); process.exit(0) }, dur * 1000 + 200)