Square wave synth gubbins
I designed a PCB to genereate 8 octaves of square waves for my jankó synth, but because the rest of the instrument doesn't exist yet, this array basically functions as a standalone MIDI square wave synth for now.
With each board generating 8 octaves of one note, and 12 boards, 96 notes of the chromatic scale are generated simultaneously. These are gated to the output with simple AND gates (which I can get away with because I'm dealing with square waves), which are in turn controlled by shift registers.
The lowest board is tuned to an F instead of the default lowest MIDI note of a C because the pitch range worked out a bit better.