Fresh Tonal Quality - Page 5

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In music, timbre, also timber (French, IPA /'tmb?r/ as in the first two syllables of tambourine), is the quality of a musical note or sound which distinguishes different types of sound production or musical instruments. The physical characteristics of sound which are used in the determination of timbre are spectrum and envelope with psychoacoustics or human perception also determining the perceived quality of a sound as the "sound color". Timbre is what, with a little practice, people use to pick out the saxophone from the trumpet in a jazz group or the flute from the violin in an orchestra, even if they are playing notes at the same pitch and amplitude (or notes which are otherwise equal). Timbre has been called the psychoacoustician's waste-basket as it can denote so many apparently unrelated aspects of a sound.

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Terms

Tone quality is also used for timbre. Helmholtz used the German Klangfarbe (tone color), Tyndall proposed its English translation clangtint, and both terms were disapproved of by Alexander Ellis who also discredits register and color for their pre-existing English meanings (Erickson 1975, p.7). Though the phrase tone color is often used as a synonym for timbre, colors of the optical spectrum are not generally explicitly associated with particular sounds. Rather, the sound of an instrument may be described with words like "warm" or "harsh" or other terms, perhaps suggesting that tone color has more in common with the sense of touch than of sight. People who experience synaesthesia, however, may see certain colors when they hear particular instruments.

American Standards Association definition

The American Standards Association defines timbre as "[...] that attribute of sensation in terms of which a listener can judge that two sounds having the same loudness and pitch are dissimilar". A note to the 1960 definition (p.45) adds that "timbre depends primarily upon the spectrum of the stimulus, but it also depends upon the waveform, the sound pressure, the frequency location of the spectrum, and the temporal characteristics of the stimulus."

Attributes

J.F. Schouten (1968, p.42) describes the "elusive attributes of timbre" as "determined by at least five major acoustic parameters" which Robert Erickson (1975) finds "scaled to the concerns of much contemporary music":

The range between tonal and noiselike character. The spectral envelope. The time envelope in terms of rise, duration, and decay. The changes both of spectral envelope (formant-glide) and fundamental frequency (micro-intonation).
1. The prefix, an onset of a sound quite dissimilar to the ensuing lasting vibration.

Spectra

Each note produced by a musical instrument is made of a number of distinct frequencies, measured in hertz (Hz). The lowest frequency is called the fundamental and the pitch produced by this frequency is used to name the note. For example, in western music, instruments are normally tuned to A = 440 Hz.

However, the richness of the sound is produced by the combination of this fundamental with a series of harmonics and/or partials (also collectively called overtones). Most western instruments produce harmonic sounds, and these can be calculated by multiplying the fundamental by an increasing series of numbers - x2, x3, x4, etc (whole number multiples). However, many instruments produce inharmonic tones, and may contain overtones which are not whole number multiples, these being the partials.

Therefore, when the orchestral tuning note is played, the sound is a combination of 440 Hz, 880 Hz, 1320 Hz, 1760 Hz and so on. The balance of the amplitudes of the different frequencies is responsible for giving each instrument its characteristic sound, which is exploited by FM synthesis.

William Sethares (2004) wrote that just intonation and the western equal tempered scale are derived from the harmonic spectra/timbre of most western instruments. Similarly the specific inharmonic timbre of Thai metallophones would produce the seven tone near equal temperament they do indeed employ, and the five note sometimes near equal tempered slendro scale provides the most consonance in the combination of the inharmonic spectra of Balinese metallophones with harmonic instruments such as the stringed rebab.

Envelope

The timbre of a sound is also greatly effected by the following factors: attack or interonset interval, decay, sustain, release, and transients. Attack, decay, sustain, and release are thus all common controls on samplers. For instance, if one takes the attack off of the sound of a piano or trumpet, one much less readily identifies the sound correctly, since the sound of the hammer hitting the strings or the first blat of the players lips are highly characteristic of those instruments.

There are two additional points that should be noted:

The fundamental is not necessarily the strongest component of the overall sound. However, it is implied by the existence of the harmonic series - the A above would be distinguishable from the one an octave below (220 Hz, 440 Hz, 660 Hz, 880 Hz) by the presence of the third harmonic, even if the fundamental were indistinct. Similarly, a pitch is often inferred from non-harmonic spectra, supposedly through a mapping process, an attempt to find the closest harmonic fit.
1. It is possible to add artificial 'subharmonics' to the sound using electronic effects but, again, this does not affect the naming of the note.

In music

Timbre is often cited as one of the fundamental aspects of music. Formally, timbre and other factors are usually secondary to pitch. "To a marked degree the music of Debussy elevates timbre to an unprecedented structural status; already in L'Apres-midi d'un Faune the color of flute and harp functions referentially," according to Jim Samson (1977). Surpassing Debussy is Klangfarbenmelodie and surpassing that the use of sound masses.

Erickson (ibid, p.6) gives a table of subjective experiences and related physical phenomena based on Schouten's five attributes:

Often listeners are able to identify the timbre of an instrument, for instance a clarinet, even across "conditions of changing pitch and loudness, in different environments and with different players." In the case of the clarinet an acoustic analysis of the waveforms shows they are irregular enough to suggest three instruments rather than one. David Luce (1963, p.17) suggests that this implies "certain strong regularities in the acoustic waveform of the above instruments must exist which are invariant with respect to the above variables." However, Robert Erickson argues that there are few regularities and they do not explain our "powers of recognition and identification." He suggests the borrowing from studies of vision and visual perception the concept of subjective constancy. (Erickson 1975, p.11)

See also

• Formant

Further reading

Stephen David Beck. "Designing Acoustically Viable Instruments in Csound" in Boulanger, Richard. The Csound Book.
• Paolo Prandoni, then graduate student, wrote two fascinating papers on timbre, available here: http://lcavwww.epfl.ch/~prandoni/timbre.html

Sources

Erickson, Robert (1975). Sound Structure in Music. University of California Press. ISBN 0520023765.
American Standards Association (1960). American Standard Acoustical Terminology. New York. Definition 12.9, Timbre, p.45. Luce, David A. (1963). "Physical Correlates of Nonpercussive Musical Instrument Tones", Ph.D. dissertation. MIT.
• Schouten, J. F. (1968). "The Perception of Timbre". Reports of the 6th International Congress on Acoustics, Tokyo, GP-6-2. Pp. 35-44, 90.
Samson, Jim (1977). Music in Transition: A Study of Tonal Expansion and Atonality, 1900-1920. New York: W.W. Norton & Company. ISBN 0393021939.
• Sethares, William (2004). Tuning, Timbre, Spectrum, Scale. ISBN 354076173X.