The Well-Tempered Clavier (German: Das Wohltemperierte Klavier), BWV 846–893, is a collection of solo keyboard music composed by Johann Sebastian Bach. He gave the title to a book of 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”. Bach later compiled a second book of the same kind, dated 1742, with the title Twenty-four Preludes and Fugues. The two works are now considered to make up a single work, The Well-Tempered Clavier, or “the 48”, and are referred to as The Well-Tempered Clavier, Book I and The Well-Tempered Clavier, Book II, respectively. This collection is generally regarded as being among the most influential works in the history of Western classical music.