音量調整

import convertMidiNoteToFrequency from '/src/convertMidiNoteToFrequency'
​
const audioContext = new AudioContext()
const destination = audioContext.destination
​
const MidiNoteArray = [60, 64, 67, 71]
​
const oscArray = MidiNoteArray.map(frequency => {
  const osc = audioContext.createOscillator()
  osc.frequency.value = convertMidiNoteToFrequency(frequency)
​
  // 音量調節用の nord
  const gain = audioContext.createGain()
​
  // 1が default の値なので、それより下げる
  gain.gain.value = 0.2
  // osc -> gain -> destination
  // となるようにつなぐ
  osc.connect(gain)
  gain.connect(destination)
​
  return osc
})
​
const now = audioContext.currentTime
​
oscArray.forEach((osc, index) => {
  osc.start(now + index)
})
​
setInterval(() => {
  oscArray.forEach(osc => osc.stop())
}, 6000)