A long time ago I saw a documentary in Jr High about a scientist in the late 1800’s or early 1900’s who invented this “magic stick”. It looked like a metal rod placed vertically and when he put his hand near the stick it made a noise. The closer his hand was to the stick the higher the pitch and the further his hand was the lower the pitch. I have no idea who this man was, what his invention was called or even the class I saw it in.
If it helps he used to demonstrate this for his scientific audience by playing songs with it.