Musical instrument classification
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At various times, and in various cultures, various schemes of musical instrument classification have been used.
The most commonly used system in use in the west today divides instruments into string instruments, woodwind instruments, brass instruments and percussion instruments. However other ones have been devised, and some cultures also use different schemes.
The oldest known scheme of classifying instruments is Chinese and dates from the 3rd millennium BC. It groups instruments according to what they are made out of. All instruments made out of stone are in one group, all those made out of wood in another, those made out of silk are in a third, and all those made of bamboo in the 4th, as recorded in the Yo Chi (record of ritual music and dance), compiled from sources of the Chou period (9th-5th centuries BC), and corresponding to the 4 seasons and 4 winds (Kartomi, 1990).
The 8-fold system of pa yin ("8 sounds"), from the same source, occurred gradually, and in the legendary Emperor Shun's time (3rd millennium BC) it is believed to have been presented in the following order: metal (chin), stone (shih), silk (ssu), bamboo (chu), gourd (p'ao), clay (t'u), leather (ko), and wood (mu) classes, and it correlated to the 8 seasons and 8 winds of Chinese culture, autumn and west, autumn-winter and NW, summer and south, spring and east, winter-spring and NE, summer-autumn and SW, winter and north, and spring-summer and SE, respectively (Kartomi, 1990).
However, the Chou-Li (Programs of Chou), an anonymous treatise compiled from earlier sources in about the 2nd century BC, had the following order: metal, stone, clay, leather, silk, wood, gourd, and bamboo. The same order was presented in the Tso Chuan (Tso Commentary), attributed to Tso Chiu-Ming, probably compiled in the 4th century BC (Kartomi, 1990).
Much later, Ming dynasty (1300s-1600) scholar Chu Tsai Yu recognized 3 groups: those instruments using muscle power or used for musical accompaniment, those that are blown, and those that are rhythmic, a scheme which was probably the 1st of scholarly type, the other earlier ones being traditional, folk taxonomies. (Margaret Kartomi, 2011, Upward and Downward Classifications of Musical Instruments-musicology.ff,cuni.cz)
More usually, instruments are classified according to how the sound is initially produced (regardless of post-processing, i.e. an electric guitar is still a string-instrument regardless of what analog or digital/computational post-processing effects pedals may be used with it).
Strings, percussion, and wind 
The system used in the west today, dividing instruments into wind, strings, and percussion, is of Greek origin (in the Hellenistic period, prominent proponents being Nicomachus and Porphyry). The scheme was later expanded by Martin Agricola, who distinguished plucked string instruments, such as guitars, from bowed string instruments, such as violins. Classical musicians today do not always maintain this division (although plucked strings are grouped separately from bowed strings in sheet music), but there is a distinction made between wind instruments with a reed (woodwind instruments) and wind instruments where the air is set in motion directly by the lips (brass instruments).
There are, however, problems with this system. Some rarely seen and non-western instruments do not fit very neatly into it. The serpent, for example, an old instrument rarely seen nowadays, ought to be classified as a brass instrument, as a column of air is set in motion by the lips. However, it looks more like a woodwind instrument, and is closer to one in many ways, having finger-holes to control pitch, rather than valves. There are also problems with classifying certain keyboard instruments. For example, the piano has strings, but they are struck by hammers, so it is not clear whether it should be classified as a string instrument or a percussion instrument. For this reason, keyboard instruments are often regarded as inhabiting a category of their own, including all instruments played by a keyboard, whether they have struck strings (like the piano), plucked strings (like the harpsichord) or no strings at all (like the celesta). It might be said that with these extra categories, the classical system of instrument classification focuses less on the fundamental way in which instruments produce sound, and more on the technique required to play them.
Various names have been assigned to these 3 traditional Western groupings (On Concepts and Classifications of Musical Instruments, Margaret Kartomi, 1990, U. of Chicago Press, pp. 136–138, 157, and notes for Chp. 10):
Boethius (5th and 6th centuries AD) labelled them intensione ut nervis, spiritu ut tibiis ("breath in the tube"), and percussione;
Cassiodorus, a younger contemporary of the above, used the names tensibilia, percussionalia, and inflatilia;
Roger Bacon (13th century) dubbed them tensilia, inflativa, and percussionalia;
Ugolino da Orvieto (14th and 15th centuries) called them intensione ut nervis, spiritu ut tibiis, and percussione;
Sebastien de Brossard (1703) referred to them as enchorda or entata (but only for instruments with several strings), pneumatica or empneousta, and krusta (from the Greek for hit or strike) or pulsatilia (for percussives);
Filippo Bonanni (1722) used vernacular names: sonori per il fiato, sonori per la tensione, and sonori per la percussione;
Joseph Majer (1732) called them pneumatica, pulsatilia (percussives including plucked instruments), and fidicina (from fidula, fiddle) (for bowed instruments);
Johann Eisel (1738) dubbed them pneumatica, pulsatilia, and fidicina;
Johannes de Muris (1784) used the terms chordalia, foraminalia (from foramina, "bore" in reference to the bored tubes), and vasalia (for "vessels");
Regino of Prum (1784) called them tensibile, inflatile, and percussionabile.
Turkish encyclopedist Hadji Khalifa (1600s) also recognized the same 3 classes in his Kashf al-zunun an asami al-kutub wa-funun ("clarification and conjecture about the names of books and sciences"), a treatise on the origin and construction of musical instruments. but this was exceptional for Near Eastern writers as they mostly ignored the percussion group as did early Hellenistic Greeks, the Near Eastern culture traditionally and that period of Greek history having low regard for that group (Kartomi, 1990).
The T'boli of Mindanao use the same 3 categories as well, but group the strings (t'duk) with the winds (nawa) together based on a gentleness (lemnoy) -strength (megel) dichotomy, regarding the percussion group (tembol) as strong and the winds-strings group as gentle. The division pervades T'boli thought about cosmology, social characters of men and women, and artistic styles (Kartomi, 1990).
Mahillon and Hornbostel-Sachs systems 
An ancient system of Indian origin, dating from the 4th or 3rd century BC, in the Natya Shastra, a theoretical treatise on music and dramaturgy, by Bharata Muni, divides instruments into four main classification groups: instruments where the sound is produced by vibrating strings (tata vadya, "stretched instruments"); instruments where the sound is produced by vibrating columns of air (susira vadya, "hollow instruments"); percussion instruments made of wood or metal (ghana vadya, "solid instruments"); and percussion instruments with skin heads, or drums (avanaddha vadya,"covereed instruments"). Victor-Charles Mahillon later adopted a system very similar to this. He was the curator of the musical instrument collection of the conservatoire in Brussels, and for the 1888 catalogue of the collection divided instruments into four groups: strings, winds, drums, and other percussion. This scheme was later taken up by Erich von Hornbostel and Curt Sachs who published an extensive new scheme for classication in Zeitschrift für Ethnologie in 1914. Their scheme is widely used today, and is most often known as the Hornbostel-Sachs system (or the Sachs-Hornbostel system).
The original Sachs-Hornbostel system classified instruments into four main groups:
- idiophones, such as the xylophone, which produce sound by vibrating themselves;
- membranophones, such as drums or kazoos, which produce sound by a vibrating membrane;
- chordophones, such as the piano or cello, which produce sound by vibrating strings;
- aerophones, such as the pipe organ or oboe, which produce sound by vibrating columns of air.
Later Sachs added a fifth category, electrophones, such as theremins, which produce sound by electronic means. Within each category are many subgroups. The system has been criticised and revised over the years, but remains widely used by ethnomusicologists and organologists.
André Schaeffner 
In 1932, comparative musicologist (ethnomusicolist) André Schaeffner developed a new classification scheme that was "exhaustive, potentially covering all real and conceivable instruments".
Schaeffner's system has only two top-level categories which he denoted by Roman numerals:
- I: instruments that make sound from vibrating solids:
- II: instruments that make sound from vibrating air (such as clarinets, trumpets, or bull-roarers.
The system agrees with Mahillon and Hornbostel-Sachs for chordophones, but groups percussion instruments differently.
Second-century Greek grammarian, sophist, and rhetoritician Julius Pollux, in the chapter called De Musica, in his 10-volume Onomastikon, had presented the 2-class system, percussion (including strings) and winds, which persisted in medieval and postmedieval Europe. It was used by St. Augustine (4th and 5th centuries), in his De Ordine, applying the terms rhythmic (percussion and strings), organic (winds), and adding harmonic (the human voice); Isodore of Seville (6th to 7th centuries AD); Hugh of St. Victor (12th century), also adding the voice; Magister Lambertus (13th century), adding the human voice as well; and Michael Pretorius (17th century)(Kartomi, 1990, pp. 119–21, 147).
The Kpelle of West Africa also use this system. They distinguish the struck (yàle), including both beaten and plucked, and the blown (fêe), as revealed by Ruth Stone in Let the Inside Be Sweet: the interpretation of music among the Kpelle of Liberia, 1982, Indiana U. Press (Kartomi, 1990). The yàle group is subdivided into 5 categories: instruments possessing lamellas (the sanzas); those possessing strings; those possessing a membrane (various drums); hollow wooden, iron, or bottle containers; and various rattles and bells. The Hausa, also of West Africa, classify drummers into those who beat drums and those who beat (pluck) strings (the other 4 player classes are blowers, singers, acclaimers, and talkers), as reported by Ames and King in Glossary of Hausa Music and its Social Contexts, 1971, Northwestern U. Press. Kartomi does not specify if these 2 classifications pre-date Schaeffner or Pollux. The concept, the way the person produces the sound, is human-centered, which is part of their traditional culture so presumably they at least pre-date Schaeffner.
The MSA (Multi-Dimensional Scalogram Analysis) of René Lysloff and Jim Matson (A New Approach to the Classification of Sound-Producing Instruments, Ethnomusicology, Spring/Summer, 1985, also at mywebspace.wisc.edu), using 37 variables, including characteristics of the sounding body, resonator, substructure, sympathetic vibrator, performance context, social context, and instrument tuning and construction, corroborated the taxonomy of Schaeffner, producing 2 categories, aerophones and the chordophone-membranophone-idiophone combination.
Another similar system is the 5-class, physics-based organology, which was presented in 2007 by Steve Mann (Natural Infaces for Musical Expression, Proceedings of the Conference on Interfaces for Musical Expression, pp. 118–23), comprises Gaiaphones (Chordophones, Membranophones, and Idiophones), Hydraulophones, Aerophones, Plasmaphones, and Quintephones (electrically and optically produced music), the names referring to the 5 essences, being earth, water, wind, fire, and the quintessence, thus adding 3 new categories to the Schaeffner taxonomy.
Instruments by range 
Western instruments are also often classified by their musical range in comparison with other instruments in the same family. These terms are named after singing voice classifications:
- Soprano instruments: flute, clarinet, recorder, violin, trumpet, oboe, soprano saxophone
- Alto instruments: alto flute, viola, horn, alto saxophone
- Tenor instruments: English horn, trombone, tenor saxophone
- Baritone instruments: cello, baritone horn, bass clarinet, bassoon, baritone saxophone
- Bass instruments: double bass, tuba, bass saxophone
Some instruments fall into more than one category: for example, the cello may be considered either tenor or bass, depending on how its music fits into the ensemble, and the trombone may be alto, tenor, or bass and the French horn, bass, baritone, tenor, or alto, depending on which range it is played.
Many instruments have their range as part of their name: soprano saxophone, alto saxophone, tenor saxophone, baritone saxophone, baritone horn, alto flute, bass flute, alto recorder, bass guitar, etc. Additional adjectives describe instruments above the soprano range or below the bass, for example: sopranino saxophone, contrabass clarinet.
When used in the name of an instrument, these terms are relative, describing the instrument's range in comparison to other instruments of its family and not in comparison to the human voice range or instruments of other families. For example, a bass flute's range is from C3 to F♯6, while a bass clarinet plays about one octave lower.
Other classifications 
Sometimes instruments are classified according to the materials from which they are made. For example, percussion instruments made from metal are sometimes called metallophones, while those made of stone are called lithophones. Similarly, wind instruments made from metal are often categorized as brass instruments. This idea is not limited to western practice: the ancient Chinese categorized instruments into eight categories of materials (silk, bamboo, wood, gourd, earth, stone, metal, and skin).
Sometimes instruments are classed according to the method of their construction rather than their materials. For example Lamellaphones are instruments that produced sound by the plucking of their "lamellae" or tongues—strips of metal, wood, or bamboo fixed to a sound-board or resonator. In the Hornbostel-Sachs classification of musical instruments, lamellophones are considered plucked idiophones, a category that includes various forms of jaw harp and the European mechanical music box, as well as the huge variety of African and Afro-Latin thumb pianos such as the mbira and marimbula.
Sometimes instruments are categorized according to a common use, such as signal instruments, a category which may include instruments in very different Hornbostel-Sachs categories such as trumpets, drums, and gongs. "According to social function" may be in this category or a separate one, but an example based on this criterion is Bonanni (e.g., festive, military, and religious)(Kartomi, 1990). He also classified them according to geography and whether they were past or present.
Benjamin de la Borde (1780) classified them according to ethnicity, his categories being black, Abyssinian, Chinese, Arabic, Turkisk, and Greek (Kartomi, 1990).
Instruments can also be classified according to the ensemble in which they play, or the role they play in the ensemble. For example, the horn section in popular music typically includes both brass instruments and woodwind instruments. The symphony orchestra typically has the strings in the front, the woodwinds in the middle, and the basses, woodwinds, and percussion in the back.
Major classifications done for the Indonesian ensemble, the gamelan, have been done by Jaap Kunst (1949), Martopangrawit, Poerbapangrawit, and Sumarsam ( all in 1984) (Kartomi, 1990). Kunst's taxonomy has 5 categories: nuclear theme (cantus firmus in Latin and balungan ("skeletal ramework") in Indonesian); colotomic ( a word invented by Kunst)(interpunctuating), the gongs; countermelodic; paraphrasing (panerusan), subdivided as close to the nuclear theme and ornamental filling; agogic (tempo-regulating), drums.
Martopangrawit has 2 categories, irama (the rhythm instruments) and lagu (the melodic instruments), the former corresponds to Kunst's classes 2 and 5, and the latter to Kunst's 1, 3, and 4.
Poerbapangrawit, similar to Kunst's, derives 6 categories: balungan, the saron, demung, and slenthem; rerenggan (ornamental), the gendèr, gambang, and bonang); wiletan (variable formulaic melodic), rebab and male chorus (gerong); singgetan (interpunctuating); kembang (floral), flute and female voice; jejeging wirama (tempo regulating), drums.
Samusam's scheme comprises:
an inner melodic group (lagu)(with a wide range), divided as elaborating (rebab, gerong, gendèr (a metallophone), gambang (a xylophone), pesindhen (female voice), celempung (plucked strings), suling (flute)); mediating ( between the 1st and 3rd subdivisions (bonang (gong-chimes), saron panerus(a loud metallophone); and abstracting (balungan, "melodic abstraction")( with a 1-octave range), loud and soft metallophones (saron barung, demung, and slenthem);
an outer circle, the structural group (gongs), which underlines the structure of the work;
and occupying the space outside the outer circle, the kendang, a tempo-regulating group (drums).
The gamelan is also divided into front, middle, and back, much like the symphony orchestra.
In West Africa, tribes such as the Dan, Gio, Kpelle, Hausa, Akan, and Dogon, use a uniquely human-centered system. It derives from 4 myth-based parameters: the musical instrument's nonhuman owner (spirit, mask, sorcerer, or animal), the mode of transmission to the human realm (by gift, exchange, contract, or removal), the making of the instrument by a human (according to instructions from a nonhuman, for instance), and the 1st human owner. Most instruments are said to have a nonhuman origin, but some are believed invented by humans, e.g., the xylophone and the lamellophone. (Kartomi, 1990).
An orally-transmitted Javanese taxonomy has 8 groupings (Kartomi, 1990):
ricikan dijagur ("instruments beaten with a padded hammer," e.g., suspended gongs); ricikan dithuthuk ("instruments knocked with a hard or semihard hammer," e.g., saron (similar to the glockenspiel) and gong-chimes); ricikan dikebuk ("hand-beaten instruments", e.g., kendhang (drum); ricikan dipethik ("plucked instruments"); ricikan disendal ("pulled instruments," e.g., trump harp with string mechanism); ricikan dikosok ("bowed instruments"); ricikan disebul ("blown instruments"); ricikan dikocok ("shaken instruments").
A Javanese classification transmitted in literary form is as follows (Kartomi, 1990):
ricikan prunggu/wesi ("instruements made of bronze or iron"); ricikan kulit ("leather instruments", drums); ricikan kayu ("wooden instruments"); ricikan kawat/tali ("string instruments"); ricikan bambu pring ("bamboo instruments", e.g., flutes).
This is much like the pa yin. It is suspected of being old but its age is unknown.
Minangkabau musicians (of West Sumatra) use the following taxonomy for bunyi-bunyian ("objects that sound"): dipukua ("beaten"), dipupuik ("blown), dipatiek ("plucked"), ditariek ("pulled"), digesek ("bowed"), dipusiang ("swung"). The last one is for the bull-roarer. They also distinguish instruments on the basis of origin because of sociohistorical contacts, and recognize 3 categories: Mindangkabau (Minangkabau asli), Arabic (asal Arab), and Western (asal Barat), each of these divided up according to the 5 categories. Classifying musical instruments on the basis sociohistorical factors as well as mode of sound production is common in Indonesia. (Kartomi, 1990).
The Batak of North Sumatra recognize the following classes: beaten (alat pukul or alat palu), blown (alat tiup), bowed (alat gesek), and plucked (alat petik) instruments, but their primary classification is of ensembles (Kartomi, 1990).
In 1960, German musicologist Kurt Reinhard presented a stylistic taxonomy, as opposed to a morphological one, with 2 divisions determined by either single or multiple voiced playing (Kartomi, 1990). Each of these 2 divisions was subdivided according to pitch changeability (not changeable, freely changeable, and changeable by fixed intervals), and also by tonal continuity (discontinuous (as the marimba and drums) and continuous(the friction instruments (including bowed) and the winds), making 12 categories. He also proposed classification according to whether or not they had dynamic tonal variability, a characteristic that separates whole eras (e.g., the baroque from the classical) as in the transition from the terraced dynamics of the harpsichord to the crescendo of the piano, grading by degree of absolute loudness, timbral spectra, tunability, and degree of resonance.
Al-Farabi, Arab scholar of the 10th century, also distinguished tonal duration. In 1 of his 4 schemes, in his 2-volume Kitab al-musiki al-kabir (Big Music Book, or Big Book of Music) he identified 5 classes, in order of ranking, as follows: the human voice, the bowed strings (the rebab) and winds, plucked strings, percussion, and dance, the 1st 3 pointed out as having continuous tone.
Ibn Sina, Persian scholar of the 11th century, presented a scheme in his Kitab al-najat (Book of the delivery), making the same distinction, having 2 classes. In his Kitab al-shifa (Book of soul healing), he proposed another taxonomy, this one having 5 classes: fretted instruments, unfretted (open) stringed, lyres and harps, bowed stringed, wind (reeds and some other woodwinds, such as the flute and bagpipe), other wind instrumets such as the organ, and the stick-struck santur (a board zither). The distinction between fretted and open was in classic Arab fashion.
See also 
- List of musical instruments
- Classification of percussion instruments
- Musical instruments (Section Classification)
- Signal instrument
- The History of Musical Instruments, C. Sachs, Norton, New York, 1940
- Kartomi, page 176, "On Concepts and Classifications of Musical Instruments", by Margaret J. Kartomi, University of Chicago Press, Chicago Studies in Ethnomusicology (CSE), 1990