[madcaptenor]

Any idea how they generate these? It seems like you could unroll a piano roll, scan it optically, and generate MIDI from it, but I'm having trouble searching because "MIDI" + "piano roll" leads only to piano rolls in digital audio workstations.

[madcaptenor]

Looks like the magic word is "digitize", and yes, it's a thing - see e. g. https://ccrma.stanford.edu/~kittyshi/pianoroll/pianoroll.htm...