Well-Tempered Clavier

''The Well-Tempered Clavier'', BWV 846–893, consists of two sets of preludes and fugues in all 24 major and minor keys for keyboard by Johann Sebastian Bach. In the composer's time, ''clavier'', meaning keyboard, referred to a variety of instruments, most typically the harpsichord or clavichord, but not excluding the organ.

The modern German spelling for the collection is ' (WTK; ). Bach gave the title ' to a book of preludes and fugues in all 24 keys, major and minor, dated 1722, composed "for the profit and use of musical youth desirous of learning, and especially for the pastime of those already skilled in this study". Some 20 years later, Bach compiled a second book of the same kind (24 pairs of preludes and fugues), which became known as ''The Well-Tempered Clavier'', Part Two (in German: ''Zweyter Theil'', modern spelling: ''Zweiter Teil'').

Modern editions usually refer to both parts as ''The Well-Tempered Clavier, Book I'' (WTC I) and ''The Well-Tempered Clavier, Book II'' (WTC II), respectively. The collection is generally regarded as one of the most important works in the history of classical music.

Composition history

Each set contains twenty-four pairs of prelude and fugue. The first pair is in C major, the second in C minor, the third in C major, the fourth in C minor, and so on. The rising chromatic pattern continues until every key has been represented, finishing with a B minor fugue. The first set was compiled in 1722 during Bach's appointment in Köthen, the second followed 20 years later in 1742 while he was in Leipzig.

Bach recycled some of the preludes and fugues from earlier sources: the 1720 ''Klavierbüchlein für Wilhelm Friedemann Bach'', for instance, contains versions of eleven of the preludes of the first book of the ''Well-Tempered Clavier''. The C major prelude and fugue in book one was originally in C major – Bach added a key signature of seven sharps and adjusted some accidentals to convert it to the required key.

In Bach's own time just one similar collection was published, by Johann Christian Schickhardt (1681–1762), whose Op. 30 ''L'alphabet de la musique'', contained 24 sonatas in all keys for flute or violin and basso continuo, and included a transposition scheme for alto recorder.

Precursors

Although the ''Well-Tempered Clavier'' was the first collection of fully worked keyboard pieces in all 24 keys, similar ideas had occurred earlier. Before the advent of modern tonality in the late 17th century, numerous composers produced collections of pieces in all seven modes: Johann Pachelbel's magnificat fugues (composed 1695–1706), Georg Muffat's ''Apparatus Musico-organisticus'' of 1690 and Johann Speth's ''Ars magna'' of 1693 for example. Furthermore, some two hundred years before Bach's time, equal temperament was realized on plucked string instruments, such as the lute and the theorbo, resulting in several collections of pieces in all keys (although the music was not yet tonal in the modern sense of the word):
* a cycle of 24 passamezzo– saltarello pairs (1567) by (c.1520–c.1577)
* 24 groups of dances, "clearly related to 12 major and 12 minor keys" (1584) by Vincenzo Galilei (c.1528–1591)
* 30 preludes for 12-course lute or theorbo by John Wilson (1595–1674)
One of the earliest keyboard composers to realize a collection of organ pieces in successive keys was (1656–1740), who compiled one such cycle of preludes in 1682. His contemporary Johann Heinrich Kittel (1652–1682) also composed a cycle of 12 organ preludes in successive keys.

J.C.F. Fischer's '' Ariadne musica neo-organoedum'' (published in 1702 and reissued 1715) is a set of 20 prelude-fugue pairs in ten major and nine minor keys and the Phrygian mode, plus five chorale-based ricercars. Bach knew the collection and borrowed some of the themes from Fischer for the ''Well-Tempered Clavier''. Other contemporary works include the treatise ''Exemplarische Organisten-Probe'' (1719) by Johann Mattheson (1681–1764), which included 48 figured bass exercises in all keys, Karl Geiringer. ''The Bach Family: Seven Generations of Creative Genius'', pp. 268–269. Oxford University Press, 1954. ''Partien auf das Clavier'' (1718) by Christoph Graupner (1683–1760) with eight suites in successive keys, and Friedrich Suppig's ''Fantasia'' from ''Labyrinthus Musicus'' (1722), a long and formulaic sectional composition ranging through all 24 keys which was intended for an enharmonic keyboard with 31 notes per octave and pure major thirds. Finally, a lost collection by