How Percussion Instruments Are Classified

Percussion is one of the largest and most varied families in music. It stretches from a simple pair of wooden claves to a set of timpani tuned with a pedal. What ties such different instruments together is the way they are played: they are struck, shaken, scraped, or rubbed. To make sense of so much variety, scholars developed classification criteria that look at the material that vibrates, the pitch of the sound, and the musical function of the instrument.

The vibrating body as a criterion

The most widely used system was published in 1914 by Erich von Hornbostel and Curt Sachs, and it sorts every instrument by what actually produces the sound. Nearly all of percussion falls into two of its four major classes.

Idiophones are instruments whose own body, rigid or elastic, vibrates without needing a string or a membrane. Cymbals, the triangle, the xylophone, claves, gongs, bells, rattles, and the caxixi all belong here. Because the whole material is the source of the sound, the choice of wood, metal, or ceramic largely determines the timbre.

Membranophones produce sound through the vibration of a membrane stretched over an opening or a shell. The snare drum, bass drum, timpani, congas, tambourine, and friction drums are all examples. Here the tension of the head, the diameter of the shell, and the spot where the drum is struck all matter.

There are also some curious borderline cases. The piano, in which hammers strike strings, is classified as a chordophone. So is the musical bow, which is struck with a small stick even though its role in a performance may be percussive. The system follows the physics of the instrument, not the gesture of the player.

Definite and indefinite pitch

A second axis, more useful for anyone playing in a group, divides percussion into two halves: instruments that produce recognizable notes and instruments that produce sounds without a precise pitch.

Instruments of definite pitch can be tuned and can play melodies or chords. They include the timpani, xylophone, marimba, vibraphone, glockenspiel, celesta, and tubular bells. They are written on the staff like any other melodic instrument and follow the same logic of key and scale.

Instruments of indefinite pitch produce noise, or a set of frequencies so complex that the ear cannot pick out a single note. Snare drum, bass drum, cymbals, triangle, tambourine, and maracas fit here. Their music is usually written on a single line, or on a few lines, where each position stands for a different instrument rather than a different pitch.

The boundary is not rigid. A drum-kit tom, for example, has an audible pitch when it is well tuned, although it is rarely used as a melodic note. Cymbals, on the other hand, have such a rich spectrum that any sense of pitch dissolves.

How the sound is set in motion

A third criterion looks at what the player does. Reference books usually distinguish these actions:

• Striking: sticks, hands, mallets, or fingers hit the instrument, as with the snare drum, congas, and xylophone.
• Shaking: the instrument is shaken and small objects inside knock against one another, as with maracas, rattles, and shakers.
• Scraping: a stick or tool is dragged across ridges, as with the guiro and the washboard.
• Rubbing: a bow or a wet fingertip sets the body vibrating in a sustained way, as with glass goblets and some vibraphone or crotales bars played with a bow.

This division explains why one family demands such different techniques in practice. Holding two mallets on a timpani has nothing in common with shaking an egg shaker.

Percussion in the orchestra and in popular groups

In a symphony orchestra, percussionists are usually divided by role. One player takes care of the timpani, which are precisely tuned and often carry a harmonic function, while the others share the snare drum, bass drum, cymbals, triangle, xylophone, and assorted accessories among themselves. A single piece can call for dozens of different instruments, and the number of players varies with the repertoire. To see how this section fits with the rest of the group, it helps to read about how bands, orchestras, and chamber ensembles differ.

In popular ensembles, percussion takes on the job of rhythmic support. A marching drumline, a Latin percussion group, and a jazz rhythm section all use different setups, yet they work on the same principle: each instrument occupies its own band of timbre and register so the parts do not blur together. A low drum marks the strong beat, a snare and smaller drums fill in, and bells and shakers form the high layer. Understanding rhythm, pulse, tempo, and meter helps you hear how those layers lock together.

Identifying an instrument with three questions

Faced with an unfamiliar percussion instrument, the quickest route is to answer three questions in order:

1. What vibrates: the whole body, a stretched membrane, or a string?
2. Does the sound have a recognizable pitch, or is it noise?
3. How does the player make it sound: striking, shaking, scraping, or rubbing?

A tambourine, for example, has a membrane and metal jingles, so it combines a membranophone and an idiophone in a single object. It is played by striking and by shaking, and it has indefinite pitch. A compound answer like this is common and does not signal a classification error. It simply reflects the hybrid nature of many instruments.

To see how the same logic applies to other groups, take a look at the overview of the main families of musical instruments.

From classification to the drum kit

The drum kit is the best example of a composite instrument. It brings together membranophones (snare, toms, bass drum) and idiophones (cymbals, hi-hat, cowbell) under the control of a single player. Each piece has its own role in register and attack, and the interaction among them creates the groove. The article on the parts of a drum kit and how they work together shows how the theoretical classification turns into a practical layout.

Why the classification matters to a player

Knowing which category an instrument belongs to is more than a matter of labels. It tells a player what to expect. An idiophone made of metal will ring on after being struck, so damping becomes part of the technique. A membranophone can be retuned by adjusting the tension of the head, which changes both pitch and character. A shaken instrument depends on the motion of the wrist far more than on the force of a strike. Composers rely on the same knowledge when they decide whether a passage needs a tuned mallet instrument for a melody, a drum for a pulse, or a cymbal roll for a swell of tension.

The classification also helps when instruments from different traditions meet. A player who has never seen a particular drum from another region can still ask the three questions above and quickly understand how it is probably held, struck, and tuned. That is exactly why scholars favor a system based on physical behavior rather than on names, which vary from place to place.

Where to Go From Here

When you listen to a recording, try to separate what is membrane, what is metal, and what is wood: timbre reveals the material. Notice too which instruments define notes and which ones only mark time. If you want to lock these ideas in, test your knowledge in the quiz.