Sounds generated by a normally monophonic instrument in which two or more pitches can be heard simultaneously. The term is customarily used to describe chordal sounds played on a woodwind or brass instrument.
Any sound created by a wind instrument consists of a simultaneous set of frequency components or partials. For a conventional monophonic tone, the partials are locked into a harmonic relationship by the interaction between the air column of the instrument and the sound generator (reed, air jet or lips). The resulting sound is perceived as a single, well-defined pitch (see Acoustics, §IV). A multiphonic sound can be achieved on a woodwind instrument by choosing an unconventional fingering pattern for which the resonant modes of the air column are not harmonically related. The player may then be able to sustain simultaneously two inharmonically related tones, each based on one of the air column modes: the interaction with the sound generator mixes the two tones, giving additional sum and difference tones. The result is a rich complex of generally inharmonic partials. Such a sound may be perceived as a stable chord with several pitches, or as a tone cluster with periodically fluctuating loudness and timbre. Multiphonic fingerings for several woodwind instruments have been tabulated by Bartolozzi (see Oboe, §II, 4(iii), esp. fig.21a.
Woodwind multiphonics are also possible using conventional fingerings, if the player uses an appropriately modified blowing technique. Similar multiphonics can be obtained on brass instruments by altering the combination of lip setting, tension and pressure known collectively as the embouchure. These multiphonics can consist of either inharmonic or harmonic partials; in the latter case, two or more of the upper partials are generated so powerfully that they stand out as individual pitches in the tone complex. A useful classification of multiphonics is provided by Castellengo.
A further technique for generating multiphonics relies on the player singing one note while playing another on the instrument. Additional sum and difference tones are created by mixing of the two tones in the sound generator of the instrument. This is the basis of the technique of horn chord playing, which has been known and practised since the 18th century.
P.R. Kirby: ‘Horn Chords: an Acoustical Problem’, MT, lxvi (1925), 811–13
W.F.H. Blandford: ‘Some Observations on “Horn Chords: an Acoustical Problem”’, MT, lxvii (1926), 128–31
B. Bartolozzi: New Sounds for Woodwinds (London, 1967, 2/1982; It. orig., 1974)
J. Backus: ‘Multiphonic Tones in the Woodwind Instruments’, Journal of the Acoustical Society of America, lxiii (1978), 591–9
M. Castellengo: ‘Sons multiphoniques aux instruments ŕ vent’, Rapport IRCAM, xxxiv (Paris, 1983)
N.H. Fletcher and T.D. Rossing: The Physics of Musical Instruments (New York, 1991, 2/1998)
V. Gibiat and M. Castellengo: ‘Period Doubling Occurrences in Wind Instrument Musical Performance’, Acustica/Acta acustica, lxxxvi (forthcoming)
MURRAY CAMPBELL