Classification System of Musical Instruments

Musical Instrument Families and the Sachs-Hornbostel System

String quartet Cello
Nerida McMurray Photography / Getty Images

Given the vast number of musical instruments in existence, instruments are grouped together to make them easier to discuss in terms of music education. The two most prominent categorization methods are family relationships and the Sachs-Hornbostel system.  

The families of musical instruments are brass, percussion, string, woodwinds, and keyboard. An instrument is categorized into a family depending on its sound, how the sound is produced and how the instrument is engineered. It is important to note that instrument families are not clear-cut distinctions as not every instrument fits squarely into a family.

A common example is a piano. A piano's sound is produced from a keyboard system that uses hammers to strike strings. Thus, the piano falls into the gray area in between string, percussion and keyboard families.

The Sachs-Hornbostel system groups instruments based on different criteria, which will be discussed below.

Instrument Family: Brass

Brass instruments produce sound when the air is blown into the device through the mouthpiece. More specifically, the musician must create a buzz-like sound when blowing in the air. This makes the air vibrate inside the instrument's tubular resonator. 

In order to play different pitches, a brass instrument features slides, valves, crooks or keys which are used to change the length of tubing. Within the brass family, instruments are divided into two groups: valved or slide.

Valved brass instruments feature valves that the musician fingers to change pitch. Valved brass instruments include the trumpet and the tuba.

Instead of valves, slide brass instruments have a slide that is used to change the length of tubing. Such instruments include the trombone and the bazooka.

Despite its namesake, not all instruments made out of brass is classified as a brass instrument. For instance, a saxophone is made of brass but does not belong to the brass family. Also, not all brass instruments are made of brass. Take the didgeridoo for instance, which belongs to the brass family but is made of wood. 

Instrument Family: Percussion

Instruments in the percussion family emit a sound when it is directly agitated by the human hand. Actions include hitting, shaking, scraping or whatever other method makes the instrument vibrate.

Considered the oldest family of musical instruments, percussion instruments are often the beat-keeper, or "heartbeat", of a musical group. But percussion instruments are not limited to only playing the rhythm. They can also produce melodies and harmonies.

Percussion instruments include maracas and  bass drum.

Instrument Family: String

As you can probably derive from its name, instruments in the string family feature strings. String instruments produce sound when its strings are plucked, strummed or hit directly by fingers. Sound can also be made when another device, such as a bow, hammer or cranking mechanism, is used to make the strings vibrate.

String instruments can be further categorized into three groups: lutes, harps, and zithers. Lutes feature a neck and a bout. Think of a guitar, violin or double bass. Harps have taut strings within a frame. Zithers are instruments with strings attached to a body. Examples of zither instruments include the piano, guqin or harpsichord. 

Instrument Family: Woodwind

Woodwind instruments create sound when the air is blown inside. This might sound like a brass instrument to you, but woodwind instruments are distinct in that air is blown in a particular way. The musician might blow air across the edge of an opening, or between two pieces. 

Depending on how air is blown, instruments in the woodwind family can be divided into flutes or reed instruments. 

Flutes are cylindrical devices that require air to blow across the edge of a hole. Flutes can then be further divided into open flutes or closed flutes.

On the other hand, reed instruments feature a mouthpiece that the musician uses to blow into. The airstream then makes a reed vibrate. Reed instruments can also be further categorized into single or double reed instruments.

Examples of woodwind instruments include the dulcian, flutefluorophore, oboe, recorder, and  saxophone.

Instrument Family: Keyboard

As you can probably guess, keyboard instruments feature a keyboard. Common instruments in the keyboard family include the piano, organ, and synthesizers.

Instrument Family: Voice

Though not an official instrument family, the human voice was the first instrument. Read more about how the human voice can produce a range of sound, including alto, baritone, bass, mezzo-soprano, soprano, and tenor.

Sachs-Hornbostel Classification System

The Sachs-Hornbostel Classification system is the most prevalent musical instrument classification system used by ethnomusicologists and organologists. The Sachs-Hornbostel system is so widely used because it applies to instruments across cultures. 

It was created by Erich Moritz von Hornbostel and Curt Sachs in 1941. They organized a system that classifies instruments based on materials used, pieces featured and how sound is produced. In the Sachs-Hornbostel system, instruments are categorized into the following groups: idiophones, membranophones, aerophones, chordophones, and electrophones.