MIDI for the CS-50/60/80 (anything that uses the YM26600 chip) is tricky because the encoder is ternary, not binary. It uses +6.5v, common and -8.5v to encode the octave, then the note. If I were making a MIDI interface for the 50 (and I might--I have a 50), I would replace both the encoder and the DAC with my own probably-Atmel-based circuit. I already did this for the CS-15, so extending it to encode 4 notes is not that much more circuit or code.
Otherwise, you would need a MIDI retrofit that uses optos or analog switches to act as a second set of contacts across each key.
--crow
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On 8/24/2014 6:20 PM, pinky pinksoir@... [yamahacs80] wrote: