Continuously generating-and-playing audio in JS isn't yet possible, except via a few experimental browser-specific APIs (Webkit-based browsers and Firefox have two different ones). But, if you want to generate a discrete portion of sound (e.g. a few seconds), you can produce a .wav file, shove it into the DOM somewhere, and then play it back. So something like this works, but a version that changed the tones in real time as you dragged the sliders wouldn't.