Ludwig van Beethoven wrote 32 mature piano sonatas between 1795 and 1822. (He also wrote 3 juvenile sonatas at the age of 13 and one unfinished sonata, WoO. 51.) Although originally not intended to be a meaningful whole, as a set they comprise one of the most important collections of works in the history of music. Hans von Bülow called them "The New Testament" of piano literature (Johann Sebastian Bach's The Well-Tempered Clavier being "The Old Testament").