note: working simulate-able example in the link below
- circuit: tinkercad (basically cad for kids i have no time, update: not yet update the CAD to the latest design)
- a midi file, optional but it might affect performance if note hold for too long (intentional), and also no stacking note, no complex anotation, just button push and release for the best result
explain later but it is scheduling and blocking for good
apr 3:- LEDs now render in "groups", or named "probes" in the source, because I prefer so
- pins allocation are optimised so an interface like zebra cable or just stacked male-male jumpers, and beeper now plug straight on Arduino UNO without jumpers