To produce sound, all percussion instruments rely on the vibration of the entire instrument or a portion of it. The specific methods used to produce that vibration are usually used to categorize them. A further distinction between instruments is made between those that produce a consistent musical pitch and those that do not.
Percussion instruments are available in many different shapes and sizes. Drums, cymbals, bells, and chimes are just a few examples of percussion instruments. When they are struck or agitated, they all make a noise. Other highly specialized instruments, such as certain types of whistles, are occasionally classified as percussion instruments, but this is based on convenience rather than sound musical theory.
When the entire instrument vibrates, some percussion instruments produce sound. Bells and cymbals, for example, function in this way. This type of percussion instrument is typically made of a material, such as glass, that produces a distinct and distinct sound when struck. Idiophones are the name for these percussion instruments. Instruments like the xylophone, despite having parts that do not vibrate, fall into this category because each bar on the instrument vibrates completely.
The vibration of a stretched membrane produces sound in a second category of instruments. Drums are a common example of this, accounting for the majority of such instruments. Because of the central role played by a vibrating membrane, this type of instrument is called a membranophone.
Percussion instruments can be divided into tuned and untuned groups in addition to being classified by the method of sound production. Notes with a specific pitch are produced by tuned instruments. The xylophone is an excellent example of this type of instrument because each bar produces a different pitch.
However, percussion instruments do not always produce sound at the same pitch. Cymbals, for example, produce sound waves at multiple frequencies and are difficult to categorize as producing a single note. In theory, other instruments can be tuned, but this is rarely done in practice. So long as it is struck consistently, the darbuka, a type of goblet drum, can be tuned to produce a specific note with a reasonable degree of accuracy. This is not, however, the standard way of playing this type of drum.
Traditions are often built around collections of musical instruments that work well together to produce a specific type of music. One such combination is a western drum kit with snare drums, bass drum, and cymbals. Another, very different, combination is the Indonesian gamelan ensemble. These cultural ensembles offer a different way to categorize percussion instruments.