Polytimb64 is a polyfonic midi interface to connect commodore 64 to midi keyboard by means the user port. I found this project by chance on youtube https://www.youtube.com/watch?v=LIM-qxfz80c The author have made a full and comprensive guide to to build the hardware and how to use the c64 software https://notevoto.4lima.de/PolyTimb64_Main_EN.html In this repository I would share a custom PCB that in addiction to the original hardware implement a little oled display and a a midi thru connector
I'm not a musician but the softwre is very powerfull with many setting like pulse width, filter and pich modulation