Hornbostel-Sachs

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Hornbostel-Sachs (or Sachs-Hornbostel) is a system of musical instrument classification devised by Erich Moritz von Hornbostel and Curt Sachs, and first published in the Zeitschrift für Ethnologie in 1914. An English translation was published in the Galpin Society Journal in 1961. It is the most widely used system for classifying musical instruments by ethnomusicologists and organologists (people who study musical instruments).

The system is based on one devised in the late 19th century by Victor-Charles Mahillon, the curator of Brussels Conservatory's musical instrument collection. Mahillon's system was one of the first to classify according to what vibrated in the instrument to produce its sound, but was limited, for the most part, to western instruments used in classical music. The Sachs-Hornbostel system is an expansion on Mahillon's in that it is possible to classify any instrument from any culture with it.

1 Basis of the system
2 Application of the system
3 Suffixes and composite instruments
4 External link

[edit] Basis of the system

Formally, Hornbostel-Sachs is based on the Dewey Decimal classification. It has four top level classifications, with several levels below those, adding up to over 300 basic categories in all. The top two levels of the scheme, with explanations, are shown below:

1. Idiophones - sound is primarily produced by the actual body of the instrument vibrating, rather than a string, membrane, or column of air. In essence, this group includes all percussion instruments apart from drums, as well as some other instruments.
- 11. Struck idiophones - idiophones set in vibration by being struck, for example cymbals or xylophones.
- 12. Plucked idiophones (lamellophones) - idiophones set in vibration by being plucked, for example the Jew's harp or thumb piano.
- 13. Friction idiophones - idiophones which are rubbed, for example the nail violin, a bowed instrument with solid pieces of metal or wood rather than strings.
- 14. Blown idiophones - idiophones set in vibration by the movement of air, for example the Aeolsklavier, an instrument consisting of several pieces of wood which vibrate when air is blown onto them by a set of bellows.

2. Membranophones - sound is primarily produced by the vibration of a tightly stretched membrane. This group includes all drums and kazoos.
- 21. Struck drums - instruments which have a struck membrane. This includes most types of drum, such as the timpani and snare drum.
- 22. Plucked drums - these are drums with a knotted string attached to the membrane. When the string is plucked, it passes the vibration on to the membrane, which vibrates to give the sound. Some kinds of Indian drums are like this. Some commentators believe that instruments in this class ought instead to be regarded as chordophones (see below).
- 23. Friction drums - drums which are rubbed, either with the hand, a stick, or something else, rather than being struck.
- 24. Singing membranes - this group includes kazoos, instruments which do not produce noise of their own, but modify other noises by way of a vibrating membrane.

3. Chordophones - sound is primarily produced by the vibration of a string or strings. This group includes all instruments generally called string instruments in the west, as well as many (but not all) keyboard instruments, like pianos and harpsichords.
- 31. Simple chordophones - instruments which are in essence simply a string or strings and a string bearer. These instruments may have a resonator box, but removing it should not render the instrument unplayable (although it may result in quite a different sound being produced). They include the piano therefore, as well as other kinds of zithers such as the koto, and musical bows.
- 32. Composite chordophones - acoustic and electro-acoustic instruments which have a resonator as an integral part of the instrument, and solid-body electric chordophones. This includes most western string instruments, including lutes such as violins and guitars, and harps.

4. Aerophones - sound is primarily produced by vibrating air. The instrument itself does not vibrate, and there are no vibrating strings or membranes.
- 41. Free aerophones - instruments where the vibrating air is not enclosed by the instrument itself, for example an old car horn, or the bullroarer.
- 42. Wind instruments - instruments where the vibrating air is enclosed by the instrument. This group includes most of the instruments called wind instruments in the west, such as the flute or French horn, as well as many other kinds of instruments such as conch shells.

A fifth top-level group, electrophones, instruments which make sound primarily by way of electrically driven oscillators, such as theremins or synthesizers, was added later. Francis William Galpin provided such a group in his own classification system, which is closer to Mahillon than Sachs-Hornbostel. For example, in Galpin's 1937 book A Textbook of European Musical Instruments, he lists electrophones with three second-level divisions for sound generation ("by oscillation," "electro-magnetic," and "electro-static"), as well as third-level and fourth-level categories based on the control method. Sachs himself seems to have acknowledged such a separate group in his 1940 book The History of Musical Instruments, where it is listed informally on the same level as the four primary classifications. However, no official references to a proper classification of the electrophones with numerical subdivisions appear to exist, and the original 1914 version of the system did not acknowledge their existence.

[edit] Application of the system

Beyond these top two groups are several further levels of classification, so that the xylophone, for example, is in the group labelled 111.212 (periods are usually added after every third digit to make long numbers easier to read). A long classification number does not necessarily indicate the instrument is a complicated one. The bugle for instance, has the classification number 423.121.22, even though it is generally regarded as a relatively simple instrument (it is basically a bent conical tube which you blow down like a trumpet, but it does not have valves or finger-holes). The numbers in the bugle's classification indicate the following:

4 - an aerophone
42 - the vibrating air is enclosed within the instrument
423 - the player's lips cause the air to vibrate directly (as opposed to an instrument with a reed like a clarinet, or an edge-blown instrument, like a flute)
423.1 - the player's lips are the only means of changing the instrument's pitch (that is, there are no valves as on a trumpet)
423.12 - the instrument is tubular, rather than being a conch-type instrument
423.121 - the player blows into the end of the tube, as opposed to the side of the tube
423.121.2 - the tube is bent or folded, as opposed to straight
423.121.22 - the instrument has a mouthpiece

423.121.22 does not uniquely identify the bugle, but rather identifies the bugle as a certain kind of instrument which has much in common with other instruments in the same class. Another instrument classified as 423.121.22 is the bronze lur, an instrument dating back to the Bronze Age.

[edit] Suffixes and composite instruments

After the number described above, a number of suffixes may be appended. An 8 indicates that the instrument has a keyboard attached, while a 9 indicates the instrument is mechanically driven. In addition to these, there are a number of suffixes unique to each of the top-level groups indicating details not considered crucial to the fundamental nature of the instrument. In the membranophone class, for instance, suffixes can indicate whether the skin of a drum is glued, nailed or tied to its body; in the chordophone class, suffixes can indicate whether the strings are plucked with fingers or plectrum, or played with a bow.

There are ways to classify instruments with this system even if they have elements from more than one group. Such instruments may have particularly long classification numbers with colons and hyphens used as well as numbers. Hornbostel and Sachs themselves cite the case of a set of bagpipes where some of the pipes are single reed (like a clarinet) and others are double reed (like the oboe). A number of similar composite instruments exist.