How it Works

The theremin is an electronic instrument invented in 1920 by Soviet physicist Lev Sergyevich Termen (anglocized Leon Theremin). It first spread to the US via a soviet propaganda tour but only entered widespread use forty years later, when American manufacturers began producing their own theremins. It produces a super unique sound, which I associate with alien movies and TV shows.

A proper theremin requires two precise technical components. First, it turns out that when your hand is by an antenna which is part of a particular circuit, it causes electricity in that circuit to oscillate at a super high frequency. We want to somehow use this signal to get a low-frequency (audible) pitch. To do this, the theremin has a fixed oscillator that's always at the same high frequency, and subtracting it from the antenna signal causes a lower-frequency wave to result due to destructive interference. This is exactly what a radio does in your car when you change channels---you 'tune' the fixed oscillator to be close to the wavelenth of your preferred radio channel, so it can get an audible frequency out at the end.

Second, you need to be able to convert this oscillation into a directive for the speaker to play the desired pitch. In my project, both of these components are abstracted to generic HETERODYNE and ASSEMBLE modules. The complete circuit is below:

With the signal collected by my ESP-32, I post the information to a webpage that can be accessed by anyone on the same network. With this, a page on my website running a space-themed arcade game constantly updates the vertical velocity of the protagonist sprite based on its most recent reading from the theremin.

—Thomas