Beep-it, the optical theremin synthesizer designed and built by Michael Una, is now for sale at Etsy
A short video documenting the various sounds one can obtain from this wondrous device can be seen here
For those who know their way around the 555, this is half of an “Atari Punk Console,” or APC as the kids call it these days. I chose to go with the single oscillator because it offers more stable control. The values in the circuit have been adjusted to obtain maximum useable range.