Player pianos work via a vacuum, where air is sucked through a few pin points in a piano roll with a bellows. A series of pipes leading to each key translate these small holes into notes.

A while back, [Jacob] played around with a player piano. After feeding a roll into the machine and trying ... resulting MIDI file isn’t in the right key, but that’s easily fixed by anyone ...

tracks need one, but when you're staring at that blank piano roll ... 1: Find your key The first step is to determine the key ...