Magic.

Well, not magic, but something about feeding a MIDI into the printer. Except, as the creator said yesterday:

The MIDI files have to be edited a bit to be played on the printer: some channels need to be disabled (percussion stuff), some are transposed to avoid exceeding the frequency limit. Also the volume of the individual instruments never fits when the original settings are used.

Whatever the fuck that means. Survivor, man.

Here is a Dot Matrix Printer Playing "Eye of the Tiger"