There is something appealing about controlling a real mechanical tune with electronics. This assembly plays Canon in D using a music-box mechanism, while exposing a simple electrical interface for starting and changing its speed.

Apply 3–5V between EN and GND to run it. PWM on EN changes the tempo, so an external controller can connect a knob or other input to the unit.

The demonstration uses an Arduino and a rotary encoder for start/stop and speed control. It is a useful way to explore an interface where a digital input produces physical musical motion rather than playback from an audio file.

Documentation: https://www.questwiseventures.com/products/canon-in-d-chorus-mechanical-music-box-breakout