J. S. Bach gave the title “Das Wohltemperirte Clavier” to a book of his preludes and fugues in all 24 major and minor keys, 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, 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 being among the most important works in the history of classical music.
Here is pianist Andras Schiff to play #21 from this collection:
