@Lugia thank you so much for your suggestion!

I am sure there are no aftertouch nor velocity sensors on the keyboard unit. just a switch matrix where you can track keyDown and keyUp of each key.
The "keyboard latch" looks interesting! but having an additional CV pitch out jack i could make a polyphonic CV keyboard which seems to be not that easy.
But i will give it a try (at least on the breadboard).

I also like your pedal idea! i didn't think of that.

Yesterday i started to create the frontplate for the keyboard unit. Due to some plastic structures of the original housing there is less space left than i thought before.

Anyway - thank you!!!

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