I think I was barely four years old when I discovered a machine. I could put thin black discs that had a hole in the center on a platform that spun. You could touch it and interrupt its function. There was a black arm, with a small sharp pin at the end, that could reach the black disc. There was a switch that you could push which started everything moving. Move the black arm to the black disc and set it down. A wondrous and beautiful sound came from this thing.