I finally managed to (sort of) complete the finger drum I started to build some years ago (but still there's room for improvements). It has two independent circuit boards, one of which is a 56 in MegaDrum and the other one controls the one octave keyboard at the top of the body.
Here's the very first time I used it and the video ended up on Drum Talk TV (the leading online drum content provider today) with a direct reference to megadrum.info in the description:
https://www.facebook.com/DrumTalkTV/videos/vb.397785253633478/986435161435148/?type=2&theater
Endre
https://www.youtube.com/channel/UCMc5rSEpm3FqC8cEEAQxe6g