Jörg shares another unusual approach to sound circuits with this mini optical organ, inspired by the legendary Optigan keyboard instrument -

my instrument generates the tone with a light depended resistor which kann be controlled by an LED. the speed and patterns on the disc determine the frequency and shape of the resulting wave form.
currently it has 8 keys (8 different pitches) and a manual pitch bend.

the instrument was made from an old cd-walkman 8 LDRs & 8 LEDs plus some passive components, 8 switches and voltage regulator.

Looks like a great use for that old CD drive in the junk bin. Printing and experimenting with new disc designs would likely be a lot of fun. Currently there’s not much info available for the project, but checking out the schematic for the optical ‘theremin’ could be an easy starting point.

Update: The project has been updated with Processing sketch, disc patterns for print, and surprisingly simple schematic -