I finally fixed the yellow buttons. It is now possible to create patterns by pressing the buttons representing time subdivisions just like most drum machines. This gives a proper user interface for assembling beats live.

I'll post a demo video soon.

Next, I'll work on BPM consistency and the potentiometers interface to control BPM. At this point, I regret using the potentiometers for controlling BPM instead of the small buttons. I'm even considering changing the BPM control to the buttons.