Here is a toy my father, a radio amateur, was soldering. What is this tricky device? This is a theremin. A bit of history, of course, needs to be told. The first theremin was created in 1908 by the Russian scientist and musician Termen, from which he got his name. The principle of operation is simple: depending on the light, the device makes peculiar sounds. Thus, it can be considered the first musical power tool.What my father did is not really a real thing, it's probably a toy on a photoresistor, but still interesting. This is due to the fact that the sound that is produced at the output is polyphonic, and the Theremin Theremin was monophonic. Making this miracle is not a very complicated device. You only need to go to the nearest radio engineering store and buy all the necessary parts, and the price to be honest is not that high.Or you can disassemble your old Chinese tape recorder, where you will find half the details.