Code, download links, and more details on my website:
https://www.devinejohnny.com/

This video describes how I turned a Music Maker lap harp and xylophone that play MIDI songs with Arduino.

The instruments are mounted with laser cut plywood and 3D printed parts. The design for these parts was done in Autodesk Fusion 360. I used a BOSS laser and Prusa MK3s printer. The notes on each instruments are struck by 5V solenoids purchased from Digikey.com. The instruments are run with Arduino boards (an Uno for the harp and Mega for the xylophone).

MIDI signals are sent to the Arduino boards over USB from a connected computer. The computer has a digital audio workstation (LMMS in this case) playing MIDI songs. Software on the computer (called loopMIDI) creates virtual ports so these signals can be passed to another piece of software (called Hairless MIDI) that creates a serial bridge to the Arduinos.