This is why we have code tags. It stops the forum software converting array indexes into italic tags.
Oops. I only added code tags after rereading my own response and seeing no 's didn't occur to me that I had put them in and that they were the reason for the italics, same for the OP I guess.
Back on topic -
I have been messing around with my hacked keyboard, its still monophonic but by racing through the active tones at varying speeds I get a basic chord effect or arppegio's either way the monophonic version is much more interesting than I expected.
I will share the schematic and code shortly, the code should be easy enough to adapt to another instrument if the OP wants to experiment.
Duane B