I believe these came out around 1968 and were popular because of the funky, almost spooky sounds. Power it on, and an internal fan blows up the reeds where the touch of a key releases the air to make sound- similar to a pipe organ. This unit works overall, except the low E key makes no sound and the low A has a chipped key. It has a bit of an air leak somewhere because it makes a sound like a reed won't turn off. Its a low volume sound and doesn't affect the play-ability of the unit. The round disk on the bottom is the volume that works fine. Has duct tape on it (possibly cracked plastic).