After some probing around the test pads while playing with the keyboard’s sustain pedal, [adriangin] found what looked like a MIDI signal between two ICs, but at a non-standard bitrate.

[FuseBox2R] decided to make it a reality, and wrote tool for converting MIDI tracks to G-code that uses the buzzer on your 3D printer. The tool is up on GitHub, and uses the M300 speaker command ...