Here’s something different – Andrew Benson’s battery-powered wrist synth, aka the Whisper Synth:
Here’s another video of the whisper synth in action. I tweaked the circuit a little bit to make the sound a little louder, and am using a 9v battery now with a 7805 regulator to power it. The little lithium coin cells didn’t seem to have enough power to run the sound. The carrier frequency pot appears to have a little bit of a shorting problem but I kinda like the unpredictability.