however if I was to build it again I would replace the main tone control with a slider, something like a cross fader, no technical reason I just think it would workout nicely - set the sound with the pots, then jam with the slider.
I was thinking about that some last night. I don't know how this works, but something like what's used in the Hiwatt Echo Theremin
would be cool. Some comenters at music sites have complained that pitch control is difficult with that. I don't know, I've listened to some samples, and it sounded cool, but then it was being used more as a sound effect than an instrument.