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 referred to a variety of stringed keyboard instruments, most typically the harpsichord or clavichord, but not excluding the organ, although it is not a stringed keyboard.

The modern German spelling for the collection is Das wohltemperierte Klavier (WTK; German pronunciation: [das ˌvoːlˌtɛmpəˈʁiːɐ̯tə klaˈviːɐ̯]). Bach gave the title Das Wohltemperirte Clavier 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 1 (WTC 1) and The Well-Tempered Clavier, Book 2 (WTC 2), respectively.^[1] The collection is generally regarded as one of the most important works in the history of classical music.^[2]

Composition history

Each set contains 24 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, and 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 (circa 1735) contained 24 sonatas in all keys for flute or violin and basso continuo, and included a transposition scheme for alto recorder.^[3]

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 Giacomo Gorzanis [it] (c. 1520~1577)^[4]
• 24 groups of dances, "clearly related to 12 major and 12 minor keys" (1584) by Vincenzo Galilei (c. 1528–1591)^{[5][failed verification]}
• 30 preludes for 12 course lute or theorbo by John Wilson (1595–1674)^{[6][failed verification][7][failed verification]}

One of the earliest keyboard composers to realize a collection of organ pieces in successive keys was Daniel Croner (1656–1740), who compiled one such cycle of preludes in 1682.^[8][9] His contemporary Johann Heinrich Kittel (1652–1682) also composed a cycle of 12 organ preludes in successive keys.^[10]

J.C.F. Fischer's Ariadne musica neo-organoedum (published in 1702 and reissued 1715) is a set of 20 prelude and 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.^[11] Other contemporary works include the treatise Exemplarische Organisten-Probe (1719) by Johann Mattheson (1681–1764), which included 48 figured bass exercises in all keys,^[12] Partien auf das Clavier (1718) by Christoph Graupner (1683–1760) with eight suites in successive keys,^[13] 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 both 31 notes per octave and pure major thirds.^[12][14] Finally, a lost collection by Johann Pachelbel (1653–1706), Fugen und Praeambuln über die gewöhnlichsten Tonos figuratos (announced 1704), may have included prelude-fugue pairs in all keys or modes.^[15]

It was long believed that Bach had taken the title The Well-Tempered Clavier from a similarly named set of 24 Preludes and Fugues in all the keys, for which a manuscript dated 1689 was found in the library of the Brussels Conservatoire. It was later shown that this was the work of a composer who was not even born in 1689: Bernhard Christian Weber (1 December 1712 – 5 February 1758). In fact, it was written in 1745–1750 in imitation of Bach's prior example.^[16][17]

Intended tuning

Bach's title suggests that he had written for a 12 note tuning system, in which all keys sounded in tune (called a "circulating temperament" or a "well temperament"). One of the opposing systems in Bach's day was meantone temperament in which keys with many accidentals sound out of tune on keyboards limited to 12 pitches per octave. Bach would have been familiar with different tuning systems, and in particular as an organist would have played instruments tuned to a meantone system.

During much of the 20th century it was presumed, possibly mistakenly, that Bach intended equal temperament; after Bach's death it became popular as the standard keyboard tuning, and had been described by theorists and musicians for at least a century before Bach's birth. Evidence for this belief is found in the fact that in W.T.C. Book 1, Bach paired the E♭ minor prelude (6 flats) with its enharmonic key of D♯ minor (6 sharps) for the following fugue. This pairs the most tonally remote enharmonic keys – at the point opposite C major on the circle of fifths, where the flat arm and sharp arm cross each other. Any unbroken performance of the pair would have required both of these enharmonic keys to sound identically tuned, implying equal temperament for this pair, as musicologists expect the entire piece to be played as a single performance.

Accounts of Bach's own tuning practice are few and inexact. The three most cited sources are Forkel, Bach's first biographer; Friedrich Wilhelm Marpurg, who received information from Bach's sons and pupils; and Johann Kirnberger, one of those pupils. Despite the presumption of equal temperament, research has continued into various unequal systems contemporary with Bach's career; there is debate whether Bach might have meant a range of similar temperaments, perhaps altered slightly in practice from piece to piece, or possibly some single, specific, "well-tempered" solution for all purposes. Modern scholars suggest some form of unequal well temperament instead of equal temperament.^[18]

Forkel reports that Bach tuned his own harpsichords and clavichords and found other people's tunings unsatisfactory, and also that Bach's personal tuning system allowed him to play in all keys, and to modulate into distant keys almost without the listeners noticing. In the course of a heated debate, Marpurg and Kirnberger appear to agree that Bach required all the major thirds to be sharper than pure – which is not very informative, since it is essentially a prerequisite for any temperament to sound tolerable in all keys.^[19]

Johann Georg Neidhardt, writing in 1724–1732, described a range of unequal and near-equal temperaments (as well as equal temperament itself), which can be successfully used to perform some of Bach's music, and were later praised by some of Bach's pupils and associates. J.S. Bach's son Carl Philipp Emanuel Bach himself published a rather vague tuning method which was close to, but still not equal temperament: He wrote that it had only "most of" the fifths tempered, without saying which ones nor by how much.

Since 1950 there have been many other proposals and many performances of the work in different and unequal tunings, some derived from historical sources, some by modern authors. Whatever their provenances, these schemes all promote the existence of subtly different musical characters in different keys, due to the sizes of their intervals. However, they disagree as to which key receives which character:

• Herbert Anton Kellner argued from the mid-1970s until his death that esoteric considerations such as the pattern of Bach's signet ring, numerology, and more could be used to determine the correct temperament. His result is somewhat similar to Werckmeister's most familiar "correct" temperament. Kellner's temperament was widely adopted worldwide for the tuning pipe organs, and contains seven pure fifths and five  1 /5 comma fifths. It is especially effective as a moderate solution to play 17th century music, if one avoids music that requires more than two flats.
Zdroj:https://en.wikipedia.org?pojem=Well-tempered_Clavier
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