temperament, in music, the altering of certain intervals from their acoustically correct values to provide a system of tuning whereby music can move from key to key without unacceptably impure sonorities. It is particularly necessary for keyboard instruments, the pitches of which cannot be varied in performance. Many systems have been devised, going back to the late 15th cent. "Just Intonation" refers to systems in which some fifths are tuned unacceptably small so that others may be pure. "Temperament" refers to systems that distribute the impurities throughout the tuning. Of these, "Equal Temperament" divides the octave into 12 equal half-steps, leaving all intervals except the octave slightly impure. (see tuning systems).

equal temperament: see tuning systems.

In music, the adjustment of one sound source, such as a voice or string, to produce a desired pitch in relation to a given pitch, and the modification of that tuning to lessen dissonance. Tuning assures a good sound for a given pair of tones; temperament compromises the tuning to assure a good sound for any and all pairs of tones. Two vibrating strings sound best together if the ratio between their lengths can be expressed by two small whole numbers. If two strings vibrate in a ratio of 2:1, the vibrations will always coincide and so reinforce each other. But if they vibrate in a ratio of 197:100 (very close to 2:1), they will cancel each other out three times per second, creating audible “beats.” These beats are what make something sound “out of tune.” Since a tone produced by one ratio will not necessarily agree with the same tone created by repeatedly applying another ratio, either some intervals must be mistuned to allow for the perfect tuning of others or all intervals must be slightly mistuned. Before 1700, several systems were used based on the former compromise, including “just intonation”; since then, the compromise known as “equal temperament,” in which the ratios represented by each pair of adjacent notes are identical, has prevailed.

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In the psychological study of personality, an individual's characteristic or habitual inclination or mode of emotional response. The notion of temperament in this sense originated with Galen, who developed it from an earlier theory regarding the four “humours”: blood, phlegm, and black and yellow bile. The subject was taken up in the 20th century by Ernst Kretschmer and later theorists, including Margaret Mead. Today researchers emphasize physiological processes (including the endocrine and autonomic nervous systems) and culture and learning.

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