Subveillance is a software synthesiser written in Processing that features two standard oscillators (with saw, sine, square, and triangle waves), a sub oscillator, a noise oscillator, a low pass filter, a filter envelope, an amplitude envelope, an LFO modulator (which can be sent to various parameters), and most importantly, a volume knob that does one even better than Spinal Tap, and goes to twelve. I made it for a university project several months ago, and now that assessment is over it's going online.
Plug in your midi keyboard (or midi keyboard emulator). Hope it's using the same device id as mine was during development (otherwise you're gonna need to do some coding) Play some tunes and turn some knobs, make some freaky sounds. :)