The Theremin first came around in the 1920′s and provided us with a host of spooky, creepy sounds and so naturally being able to make one at home with standard electronics is a must. A standard Theremin uses two antennae for pitch and volume control. For this project, we will ignore controlling the volume and just look at controlling pitch.
IR sensors used to detect the distance between the sensor and an object are a perfect fit for a DIY Theremin because they are low cost and they are reliable enough to get the project working. The idea here is that instead of using antennas, we’ll use infrared proximity and be able to play an instrument, the IR Theremin!
Mini IR Theremin - [Link]