I didn't think this was possible, since audio editing was long claimed to be a desktop only solution (VST, Juce, Cubase, ProTools).
Very cool indeed!
(And good learning material for me, an ex game C++ tools developer -> web backend/frontend java/gwt now).
I must admit that I was pretty sceptical about it, all the way up to when I wrote a couple of lines to connect a few nodes, then I wrote a very simple pair of noteOn, noteOff functions (no envelopes, no nothing) and a tiny function to parse the MIDI key number... And when I started playing that... single sine wave without any flavor on it or effects... I loved it! The latency was great, the oscillator produced such a pleasant sound and above all... I (couldn't make this "capital-enough") have built this teeny-tiny (for me - uber-cool) instrument. :)