tuning systems, methods for assigning pitches to the twelve Western pitch names that constitute the octave. The term usually refers to this procedure in the tuning of keyboard instruments. The need for a tuning system hinges on the conflict of pitch relationships in the natural overtone series and the exigencies of musical compositional systems, specifically those utilizing the familiar diatonic scale. Chronologically, the conflict occurred in the early Renaissance when composers had an increasing desire to modulate from one key to another. Implicit in the concept of modulation is the condition of identity of intervals between corresponding scale degrees in different modes or keys. A keyboard instrument tuned to a function of any natural interval except the octave will not satisfy that condition. The Pythagorean system, derived from a scale supposedly invented by Pythagoras (c.550 B.C.), was generated by acoustically perfect fifths. It exhibited an audible difference between the interval of a semitone and the interval resulting from the subtraction of the semitone from the whole tone. The mean-tone system generated the scale with fifths just flat enough to eliminate this difference, producing a scale containing acoustically perfect thirds. Discrepancy between chromatic notes (semitones) rendered this system unsuitable for successive modulations. Equal temperament tuning, which replaced mean-tone tuning in the 18th cent. and is universally accepted for Western music today, partitions the octave into twelve equal semitones. All intervals except the octave are acoustically out of tune, but by a tolerable degree, making complex modulations and atonality possible.

tuning fork, steel instrument in the shape of a U with a short handle. When struck it produces an almost pure tone, retaining its pitch over a long period of time; thus it is a valuable aid in tuning musical instruments. It was invented in 1711 by John Shore, who jokingly called it a pitchfork.

tuning: see tuning systems.

automatic tuning control (ATC), method or device to keep a radio or television receiver automatically tuned to a desired frequency or channel. Assuming that the receiver is at least approximately tuned to the desired frequency, a circuit in the receiver develops an error voltage proportional to the degree to which the receiver is mistuned. This error voltage is then fed back to the tuning circuit in such a way that the tuning error is reduced. In most frequency modulation (FM) detectors an error voltage of this type is easily available; in television receivers extra circuits may be used to develop it. In an FM receiver, automatic frequency control (AFC) may make it difficult to receive a weak signal located near in frequency to a strong one. In tuning circuits that use frequency synthesis, in which digital circuitry, in conjunction with a crystal oscillator, produces precise signals, automatic tuning control is not necessary.

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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