I built this for a friend and had to mail it away before I could get any video.
The design is based on the classic 4093 based NAND synth, but there are some big differences on this one. There are phototransistors across pins 1 and 3 of each potentiometer to modulate things. Under the hood they are connected via small alligator clips to be removable if you get tired of them.
Basically all of the capacitors are separate from the circuit and the appropriate pins on the 4093 are brought out to header pins. That way you can 'roll your own' custom setup. There's also a simple 4 channel passive mixer that brings it all together for your output.
Annotated image here.