This trick was used as far back as the 19th century to synthesize musical tones.  The gears have 24, 27, 30, 32, 36, 40, 45, and 48 teeth, so the notes are all related by simple fractions - that makes this a just intonation scale rather than equal temperament.

There's plans and instructions on thingiverse: www.thingiverse.com/thing:6662