acoeur/themes/acoeur/assets/js/notes.js

// let freq = 440

const tons = [264, 275, 297, 316.8, 330, 352, 371.25, 396, 412.5, 440, 475.2, 495]
// const tons = [396, 417, 528. 639, 741, 852, 963]

/*
 * Play one note
 */
const note = (context, freq, counter) => {
  // console.log("Note n°", counter, freq)

  const oscil = context.createOscillator()
  oscil.type = 'sine'
  oscil.frequency.value = freq

  const gainNode = context.createGain()
  oscil.connect(gainNode)
  gainNode.connect(context.destination)

  const notesPerSecond = 5 // In Hertz
  // All are in seconds
  const start = counter / notesPerSecond
  const duration = .5

  // Increase volume
  gainNode.gain.setValueAtTime(1, start)
  oscil.start(start)

  // Decrease volume
  gainNode.gain.exponentialRampToValueAtTime(0.001, start + duration);
  oscil.stop(start + duration)
}

/*
 * Launch notes based on the current URL
 */
const launchNotes = (event, counter = 0, uuid = getUuidFromUrl()) => {
  if (counter >= uuid.length || counter >= 5) return

  const context = new (window.AudioContext || window.webkitAudioContext)();

  const freq = tons[parseInt(uuid[counter], 16) % tons.length]
  // freq *= Math.max(1, parseInt(uuid[counter], 16)) / Math.max(1, parseInt(uuid[counter + 1], 16))
  // freq = Math.min(2000, Math.round(freq))

  note(context, freq, counter)
  // note(context, freq * 2, counter)

  launchNotes(event, counter + 1, uuid)
}

// document.onclick = launchNotes