The panels were made using a subtractive Laser printing (just made that up). Basically I painted the modules black and I used a laser to removed the paint to create the image. because the modules are painted, they are far darker than the etched modules.
I'll have some more to say about these VCOs later.
I recently designed a MIDI distributor module which splits up incoming polyphonic MIDI commands into monophonic MIDI commands on separate channels. I designed it with the intention of turning my modular into a polyphonic synth. I used the Arduino atmega328. I recently rewrote the code to utilize the <MIDI.h> library.
the code uses the MIDI.h library but you also need to add my MIDIbuddy.h file