oscillator.js

var max = {
};

var elm = {
  freq: document.querySelector("#freq"),
  attack: document.querySelector("#attack"),
  decay: document.querySelector("#decay"),
  sustain: document.querySelector("#sustain"),
  release: document.querySelector("#release"),
  play: document.querySelector("#play")
};

var context = new AudioContext();
var oscillator = context.createOscillator();
oscillator.frequency.value = 146.832;
var envelope = context.createGain();
var gain = context.createGain();
gain.gain.value = 0;
var filter = context.createBiquadFilter();
filter.type = "lowpass";
filter.frequency.value = 440;

oscillator.connect(envelope);
envelope.connect(gain);
gain.connect(filter);
filter.connect(context.destination);

oscillator.start();
var playing = false;

elm.play.addEventListener("click", event =>{
  if(playing){
    gain.gain.value = 0;
  }else{
    gain.gain.value = 0.75;
    envelope.gain.value = 0;
    envelope.gain.linearRampToValueAtTime(0.8, context.currentTime + 1400);
  }
  playing = !playing;
});