A membranophone is any musical instrument which produces sound primarily by way of a vibrating stretched membrane. It is one of the four main divisions of instruments in the original Hornbostel-Sachs scheme of musical instrument classification. Most membranophones are drums. Hornbostel-Sachs divides drums into three main types:
1.) Struck drums, where the skin is hit with a stick, the hand, or something else;
2.) String drums, where a knotted string attached to the drum’s skin is pulled, passing its vibrations onto the skin;
3.) Friction drums, where some sort of rubbing motion causes the skin to vibrate. A common type has a stick passing through a hole in the skin which is pulled back and forth.