We love alternative musical interfaces.  XenonJohn’s Aetherharp uses inexpensive Sharp GP2Y0A41SK0F analog distance sensors to determine hand proximity.

Like a theremin it is played without physical contact by the performer, but using light rather than antennas to determine proximity.  XenonJohn demonstrates the project on Instructables with his Teensy 3.5-powered Aetherharp.

Eight Sharp IR sensors are each configured to determine three discrete height levels, resulting in 24 possible notes.

Teensy’s USB MIDI capabilities are then leveraged to convert the hand gestures to sound via a connected laptop, which also provides power to the device.

Code and complete instructions can be found on Instructables, and a demonstration of the instrument can be seen below.