Tuning and musical history

It is seldom realized what an important effect tuning practices have had on the development of harmony and tonality. From the 10th to the 13th century thirds and sixths—now considered consonant—were treated as dissonances simply because, according to then-current tuning methods, they were dissonances. In Pythagorean tuning, only the bare fifth and octave could provide a tolerable point of repose in music accompanied by the organ. Although just intonation permitted some harmony based on triads, the use of sharpened leading notes (the last note of the scale, leading upward into the first), which by the 16th century had caused the older system of modes to disintegrate, was made acceptable only by the use of some kind of temperament. At a later date it was the existence of lutes tuned in equal temperament that made possible the more extreme experiments in chromaticism of composers such as Luca Marenzio and Don Carlo Gesualdo. The formation of a unified orchestra was probably delayed by the simultaneous practice of two incompatible tuning systems—mean-tone for keyboard instruments, equal temperament for lutes and viols. The decline of viols and their replacement by the violin family may have been hastened by the inability of viols to play with the organ. The modern orchestra began with the Vingt-quatre Violons du Roi (Twenty-four Violins of the King) of Louis XIV, and most later Baroque music is based on a keyboard instrument with from one to 30 members of the violin family playing in mean-tone temperament. The cycle of six related keys, established in the operas of Alessandro Scarlatti and the sonatas of Arcangelo Corelli and followed closely in most of the music of J.S. Bach and George Frideric Handel, is probably a direct outcome of mean-tone temperament. Within the limits of mean-tone temperament, the six keys exhaust the chromatic compass available. On the other hand, “wolf” chords may have been deliberately introduced by Domenico Scarlatti, François Couperin, and other composers to give an added piquancy to certain harpsichord passages. Many harpsichord players, including Bach, would retune a few notes of their instruments to prepare to play a piece in a new key, shifting the “wolf” fifth to part of the scale where it would do no harm. But in organ works such temporary retuning was hardly possible. Bach’s organ tuning must have been as close to equal temperament as modern instruments are, although it is known that he was opposed to a strictly mathematical equality of intervals. By his title Well-Tempered Clavier he probably meant a kind of modified mean-tone temperament.

Enharmonic modulation, in which one note (say B♭) is treated as identical to another (say A♯) that actually has the same pitch only in equal temperament, was an exceptional device in Baroque music. But as orchestras became free of keyboard instruments and as keyboard instruments increasingly adopted equal temperament, it became a normal stock-in-trade, allowing the use of a series of key changes in one direction that eventually returns to the original key. Thus, it is not unusual for Mozart to complete the cycle of 12 keys in the course of a movement. Equal temperament permitted 19th-century composers to use the 12 notes of the chromatic scale with the utmost freedom. It also fixed those 12 notes so immutably in the Western musical consciousness that the revolutionary developments of 20th-century music, far from undermining them, have tended to perpetuate them.