Interesting, and quite responsive. Audio generation in JS that I've tinkered with elsewhere tends to seem responsive until you try to make music out of it, at which point the poor timing is painfully obvious.

At the moment this seems to just be doing basic tone generation, though -- the options are sawtooth wave vs. sine wave etc..

Things get messy when you dig into MIDI playback type features, working with samples, sound libraries, etc.. But if they can forge a clear path in that direction (but somehow not lose decent timing), that could be quite useful.