A Teensy 3.6 is used to run the show, acting as a USB-MIDI interface so the toy can be controlled by music software like Abelton. It’s connected to the toy’s buttons through a multiplexer.

1-in 6-out】The MIDI Thru-6 Box provide 1 MIDI in and 6 MIDI out midi interface. Smooth MIDI signal ... which is power by 5V DC USB power supply. It can works with most MIDI products.

Once the HIDUINO is loaded your Arduino can show up as any HID compliant device you wish, no extra drivers ... MIDI directly to/from the Arduino. Currently the project is for direct USB-MIDI ...