annyaudio.js

var ctx = new AudioContext();

var osc1 = audioCtx.createOscillator();
osc1.type = 'square';
osc1.frequency.setValueAtTime(440, ctx.currentTime);
osc1.start();

var osc2 = audioCtx.createOscillator();
osc2.type = 'square';
osc2.frequency.setValueAtTime(441, ctx.currentTime);
osc2.start();

var gainNode = audioCtx.createGain();
gainNode.gain.setValueAtTime(0.3, ctx.currentTime);
gainNode.connect(ctx.destination);

osc1.connect(gainNode);
osc2.connect(gainNode);