Timbre

In music, timbre is the quality of a musical note which distinguishes different types of musical instrument. This is why, with a little practice, you can pick out the saxophone from the trumpet in a jazz group or the flute from the violin in an orchestra.

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 as "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

The physical characteristics of sound which are used in the determination of timbre are spectrum and envelope.

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 argues in Tuning, Timbre, Spectrum, Scale 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, decay, sustain, release, and transients. 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:

  1. 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 infered from non-harmonic spectra, supposedly through a mapping process, an attempt to find the closest harmonic fit.
  2. It is possible to add artificial 'subharmonics' to the sound using electonic effects but, again, this does not affect the naming of the note.

Timbre is often cited as one of the fundamental aspects of music.



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