Draw sound waveforms with a mouse, then play the sounds with keys that vary in pitch. The frequency and phase spectrum can also be manipulated in the same way.
Mostly I want to create crude chiptunes sound effects which it can do pretty well, I think it needs more layering/modulation capability to be a bit more useful. Also most of the interesting frequencies are very near the left hand fifth of the frequency plot, an ability to zoom there and on the time waveform would be very useful- maybe doubling or tripling the amount of horizontal resolution devoted to the plots would be nice as well.
The mouse drawing code is pretty crude, it can't even interpolate between two different sampled mouse y positions yet.
I used Processing and the minim sound library which didn't directly support manipulation or viewing of phase information. The trick was to subclass fft like this: