Maryaguirre

Foundations

Instrument Families and How They Are Classified

Orchestral families and the Hornbostel–Sachs system answer different questions about the same instruments, and this library borrows from both to organise its collection.

Musicians group instruments by how they sit in an orchestra, while museums group them by how they produce sound. This guide compares the two approaches, traces the history from Mahillon’s nineteenth-century scheme to the 1914 Hornbostel–Sachs system, looks at where classification strains, and explains the six families used across the library.

Two ways of sorting the same stage

Look at a symphony orchestra’s seating plan and the sorting is done for you: strings at the front, woodwinds behind them, brass and percussion at the back. These orchestral families grew out of performance practice. They tell a conductor who plays together, who reads similar parts, and who shares a section leader. Orchestras also keep the harp and keyboards as a small extra group, as the Philharmonia Orchestra’s own instrument pages do.

Practical groupings have quirks. A Flute is commonly made of metal yet counted among the woodwinds, because its ancestors were wooden and it has long been written for alongside the reed instruments. A Saxophone has a brass body but a single reed, and is filed with the woodwinds for that reason. Such labels describe a musical role, not a physical mechanism, and a collection that spans the world needs a scheme that does not depend on the orchestra.

From wind, strings and percussion to four categories

Older European writers often used three headings: wind instruments, stringed instruments and percussion. The scheme suited the orchestra but left awkward cases. Where does a struck string belong, or a pitched drum, or a bar that rings when hit? A widely cited advance came from Victor-Charles Mahillon, a Belgian instrument-maker and curator at the Brussels Conservatoire, who in 1880 proposed four categories based on what actually vibrates: a column of air, a string, a membrane, or the solid body of the instrument.

The change looks small, but it shifted the question from how an instrument is played to how its sound begins. A Xylophone and a Timpani are both struck, yet one rings through a rigid bar and the other through a stretched skin. Under Mahillon’s logic they belong to different groups, and a Violin and a Harp land together despite being bowed and plucked.

The 1914 system

In 1914 Erich von Hornbostel and Curt Sachs published Systematik der Musikinstrumente in the Zeitschrift für Ethnologie. It built on Mahillon’s four-part idea and added a decimal notation inspired by library classification, so that each instrument receives a numbered address that narrows step by step. The aim was a framework able to describe instruments from any culture, not only European ones.

The four original classes are idiophones, membranophones, chordophones and aerophones. In an idiophone the material of the instrument itself vibrates, as in the Marimba or Vibraphone. In a membranophone a stretched skin does, as in the Drum Kit. In a chordophone one or more strings do, from the Cello to the Koto. In an aerophone air is the vibrating body, which covers the Trumpet and Oboe, and also the free-reed Accordion and Harmonica. The Piano, whose hammers strike strings, is treated as a chordophone.

Adding electricity, and revising the map

Electronic instruments did not fit any of the four classes. The English organologist Francis Galpin used the term electrophonic instruments in 1937, and Sachs placed electrophones in his scheme by 1940, making the fifth and last top-level class. Broadly, an electrophone is an instrument in which the sound originates in electrical circuits, not one that is merely amplified.

The original German text reached English readers through a translation in the Galpin Society Journal in 1961, and the system then became a standard tool of museums and ethnomusicologists. In 2011 the Musical Instrument Museums Online project issued a revised and expanded version to accommodate instruments and subdivisions that the 1914 text handled awkwardly. Historians and curators therefore speak of Hornbostel–Sachs as a living framework, not a finished one.

Why sound production travels well

The strength of a mechanism-based scheme is that it needs no assumptions about a tradition’s music. A Sitar and a Mandolin belong together as chordophones whether the listener knows Indian classical music or Italian folk ensembles, and the same holds for a Banjo and an Acoustic Guitar. Families built around the orchestra, in contrast, describe one regional tradition and stretch poorly when applied to instruments that never entered it.

That does not make the orchestral view wrong. It remains the vocabulary most readers already use, and it reflects how instruments are taught, scored and rehearsed today. The two views are best seen as maps at different scales: one drawn for the concert hall, the other for a museum gallery that holds instruments from many places, periods and living traditions.

Where the map strains

No system has a clean answer for every instrument. Scholars have criticised Hornbostel–Sachs for uneven logic between its branches, for a numbering layout that can confuse, and for the difficulty of inserting new instruments without upsetting the pattern. Hybrids are the hardest cases. The Drum Kit combines drums with metal cymbals, which are idiophones. The Berimbau is a musical bow, a chordophone, whose gourd acts as a resonator, and the pitch is altered by pressing a stone or coin against the wire.

The Electric Guitar poses a different puzzle. Its string vibrates, which suggests a chordophone, yet electronics are essential to how it is heard. Curators differ on how to handle such cases, and the honest position is that the category depends on which feature one considers decisive. Systems of this kind are tools for comparison, not laws of nature, and their usefulness lies in making hard cases visible.

How this library groups instruments

The library combines the two traditions. Its six families are Keyboard, Strings, Woodwinds, Brass, Percussion and Free-reed. They are practical groups a reader can recognise, but each entry also carries a separate tag for its sound-production route, which follows the spirit of Hornbostel–Sachs: vibrating string, air column, membrane, solid body or free reed.

Keeping the two labels apart resolves many puzzles. The Piano belongs to the Keyboard family because of how it is played, yet its production route is the vibrating string. The accordion and harmonica form the Free-reed family because their shared mechanism is more revealing than any orchestral category. The Berimbau and Electric Guitar sit with the Strings. Brass means lip-buzzed tubes, and Woodwinds includes the flute and saxophone by tradition. Readers can therefore browse by orchestral habit or by acoustic principle, and find the two views sometimes agree and sometimes do not.

Terms used in this article

Aerophone
An instrument in which vibrating air, or a reed or lips acting on air, produces the sound.
Chordophone
An instrument in which stretched strings produce the sound.
Electrophone
An instrument whose sound originates in electrical or electronic circuits.
Hybrid instrument
An instrument that combines more than one sound-production principle and so resists a single classification.
Idiophone
An instrument whose own rigid material vibrates to make the sound, such as a bar or a bell.
Membranophone
An instrument in which a stretched skin or film is the vibrating element.
Organology
The scholarly study of musical instruments, including their history, construction and classification.

References

  1. International Society for Knowledge Organization (ISKO). Hornbostel-Sachs Classification of Musical Instruments. isko.org/cyclo/hornbostel
  2. Philharmonia Orchestra. Instruments | Philharmonia. philharmonia.co.uk/explore/instruments
  3. Philharmonia Orchestra. Trumpet | Philharmonia. philharmonia.co.uk/explore/instruments/trumpet
  4. Philharmonia Orchestra. Timpani | Philharmonia. philharmonia.co.uk/explore/instruments/timpani
Published Last reviewed 985 words · 4 min read

Issued by the Atlas Musical Editorial Desk. Spotted an error? Request a correction or read the Corrections Policy.

Instruments mentioned

Follow the ideas into the entries.

Front view of a varnished golden-brown violin with two f-holes, an ebony tailpiece and fingerboard and four strings, photographed upright against a soft grey background.
Strings

Violin

The violin is the smallest and highest-pitched member of the modern violin family, with four strings tuned a fifth apart and set into vibration by a horsehair bow. It took its recognisable form in northern Italy in the sixteenth century and was refined in Cremona over the next two hundred years. It leads the orchestra, anchors the string quartet, stars in the concerto and, under the name fiddle, drives dance and folk music in many regions.

Renaissance–Baroque (1400–1750)
Rosewood grand piano with carved scroll cheek blocks, tapered turned legs on brass casters and a lyre-shaped pedal assembly, shown from the keyboard end with the lid and music desk raised against a plain white background.
Keyboard

Piano

The piano is a keyboard instrument in which felt-covered hammers strike tensioned metal strings, and in which the player shapes loudness through the speed of the touch. Devised in Italy around 1700, it grew through the eighteenth and nineteenth centuries into an iron-framed machine with a standard compass of 88 keys. It serves as solo voice, accompanist, chamber partner and orchestral colour, and it remains a working tool for composing, teaching and rehearsing in many musical traditions.

Renaissance–Baroque (1400–1750)
An old wooden xylophone with rows of pale maple bars stamped with note letters, laid in an open wooden case with its lid beside it, on a white background.
Percussion

Xylophone

A xylophone is a set of tuned wooden or synthetic bars struck with mallets. The name covers a worldwide family, from West African balafons to Javanese gambangs, and also the keyboard-layout orchestral instrument, which sounds bright, dry and penetrating and is written an octave lower than it sounds. It is distinct from the marimba, which is lower, wider and warmer.

Classical–Romantic (1750–1900)
Diatonic button accordion with a tortoiseshell-and-enamel case decorated in pink, green and blue scrollwork, pearl keys along the left side and dark leather bellows, photographed from the side against a grey studio backdrop.
Free-reed

Accordion

The accordion is a portable free-reed instrument in which the player pumps a pleated bellows to push air across metal reeds, choosing notes with keys or buttons on two sides. A patent granted in Vienna in 1829 is usually cited as its starting point, though similar instruments were being built at about the same time. It spread through migration and trade into dance, song and concert traditions on nearly every continent.

Classical–Romantic (1750–1900)
Five berimbaus laid side by side against a turquoise surface, each a curved wooden bow strung with a thin wire and fitted with a gourd resonator, some painted in bright patterns and others left natural.
Strings

Berimbau

The berimbau is a single-stringed musical bow from Brazil: a long wooden arc, a steel wire and a hollow gourd that amplifies the sound. The player strikes the wire with a thin stick while pressing a coin or stone against it and shaking a small basket rattle. Closely tied to African bows brought across the Atlantic, it leads the music of capoeira, setting the pace and mood for the game in the circle.

Classical–Romantic (1750–1900)
A pearl-white drum kit on a green rug in a recording studio, with bass drum, toms, snare, hi-hat and cymbals surrounded by microphone stands.
Percussion

Drum Kit

The drum kit gathers a bass drum, snare drum, tom-toms and cymbals around one seated player, who operates some of them with the feet. It took shape in the United States between the late 1800s and the 1930s, as the work of several percussionists was consolidated into the job of one performer. It anchors jazz, rock, pop and many other styles with pulse, accent and colour.

Modern (after 1900)

More articles

Foundations

How Instruments Make Sound

From a trembling string to a buzzing lip, every instrument turns motion into music through one of five routes, and its body decides how that sound is heard.

5 min read · Reviewed 30 September 2026
Foundations

Range, Register and Timbre Explained

Range says how high and low an instrument can go, register and tessitura say where it is comfortable, and timbre explains why the same note never sounds identical twice.

5 min read · Reviewed 30 September 2026