This project for the Raspberry Pi uses inexpensive HC-SR04 ultrasonic sensors as inputs and turns them into keys on a MIDI keyboard. There's something pretty neat about using sound to make sound. It's like fighting fire with fire, but much safer!
This project has featured on blogs from The Raspberry Pi Foundation, Adafruit, and Hackaday!
Click on this preview to see the Ultrasonic Pi Piano in action!
This repository contains documentation for creating your own Ultrasonic Pi Piano.