Michael from AcidBourbon writes, “This project is about adding a MIDI output to a vintage organ, the Korg CX-3 (famous Hammond compact organ clone). My Korg was built in 1979, so before the introduction of the General Midi standard. But tapping into the right (only three) conducting paths on the main PCB and using a level converter plus an ATTiny2313 lets you add a MIDI-Out very inexpensively.”
Details on this project, including schematic and link to the MCU firmware can be found at AcidBourbon.
Via the contact form.