Oscillator + Gain

	
	var ctx = new AudioContext();
	var osc = ctx.createOscillator();
	osc.type = "square";
	var vol = ctx.createGain();
	vol.gain.value = 0.2; // 0.0 〜 1.0
	osc.connect(vol);
	vol.connect(ctx.destination)
	osc.start(0);