Homemade synthesizer song #4

This time I use the tuning fork controlled synthesizer to make a sort of arpeggio. Another thing to notice is the keyboard with aftertouch. It is actually made really simple: The entire keyframe is on hinges and held up with two springs so that it can be pressed downwards a couple of millimeters. The edge of the frame then dips into an optocoupler fork and thereby generates a variable voltage that can control other modules.