Ex. 11-1: Fugue

No. 23 from Book I of Bach's Well-Tempered Clavier, compiled around 1722. Book I runs through all 24 keys, rising by half steps from C major; this B major pair is the second to last, just before the closing B minor.

Around this time Bach was Kapellmeister at the court of Anhalt-Cöthen. In these Cöthen years Bach wrote much of his finest instrumental music, including the Brandenburg Concertos and the solo violin sonatas and partitas.

These were also hard years in his personal life. In 1720, while Bach was away with the prince at the spa town of Carlsbad, his first wife, Maria Barbara, died and was buried before he returned home. In December 1721 he married the singer Anna Magdalena. The fair copy of Book I dates from 1722, as Bach was rebuilding his life with his new family.

B major has five sharps. In the tunings common in Bach's day, keys with this many sharps sounded badly out of tune and were rarely used. Bach put the collection together to show that with a "well-tempered" tuning, every key — even unusual ones like B major — could sound clear and in tune. This fugue is often noted for how simply and naturally Bach writes in a key once thought difficult.

Bach first wrote this piece in a shorter, simpler form, known as the Prelude and Fughetta in B major (BWV 868a). He later expanded it into the longer prelude and fugue in the collection.

The fugue is in four voices. They enter one after another — tenor, alto, soprano, bass — and later the theme is turned upside down (inversion). Even with all these voices woven closely together, the lines stay smooth and song-like. The prelude and fugue just before it, No. 22 in B-flat minor, is also in this app. (Ex. 10-1: Prelude by Johann Sebastian Bach)

From the album Bach: The Well-Tempered Clavier, Book I by Ramin Bahrami (2018)
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