[Keystone Science] recently posted a video about building a theremin — you know, the instrument that makes those strange whistles when you move your hands around it. The circuit is pretty simple (and borrowed) but we liked the way the video explains the theory and even dives into some of the math behind resonant frequencies.
The circuit uses two FETs for the oscillators. An LM386 amplifier (a Hackaday favorite) drives a speaker so you can use the instrument without external equipment. The initial build is on a breadboard, but the final build is on a PCB and has a case.
This is the kind of project that could capture a kid’s imagination — especially one with an interest in music. We don’t have anything against microcontroller projects, but a circuit like this is great for exploring oscillators, amplifiers, resonant frequencies, and other details of electronics you don’t get with a typical Arduino LED blinker.