Nitpick--Audiotool is pretty much 100% Flash, except it also seems to load a Java applet to gain MIDI access. It would be mindblowing if it were HTML5. The UI alone (especially all the little details like the correct shadows on the knobs and the wire layout, and the zoomability) would be an incredible accomplishment to draw with HTML and <canvas>. As for the synthesis, I think Audiotool predates the Web Audio API.