It may spoil a lot of DIY and development fun, but it all exists already: https://tubbutec.de/modypoly/ This Key assigner MCU contains original functions plus MIDI-IN plus MIDI-OUT plus additional chordmemory functions plus additional arpeggiator/sequencer functions
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Re: [PolySix] Replacing the Key assigner MCU
2015-12-20 by Florian Anwander