I’ve got the SN76477-based drum machine up and running, and it sounds pretty sweet:

SN76477-based drum machine prototype from Michael Una on Vimeo.

I need to work on the switching logic for the different sounds, and add in a flip-flop to increase my steps from 8 to 16. But it’s very close to being done, in this form. Next up, getting some circuit boards printed and then building it into a permanent case. And maybe getting some nice cases laser-cut.