What are membranophones?

Membranophones are a specific category of musical instruments that produce sound through vibrating membranes. This definition is fundamental to understanding this type of instrument. The vibrating membrane, typically made from materials such as animal skin or synthetic materials, is stretched across a frame and is set into motion either by striking, rubbing, or plucking. The sound is generated as the membrane vibrates, creating sound waves.

In the context of different categories of instruments, membranophones contrast with other groups. Instruments that simply produce sound by being struck—while they may include some membranophones like drums—are not limited to those utilizing membranes. Instruments made of metal can belong to other classifications such as idiophones or aerophones, and likewise for those that produce harmonic overtones. Thus, the defining feature of membranophones is their use of membranes as the primary sound-producing element, which is precisely encapsulated in the correct answer.