Piano sonatas (Beethoven)
Ludwig van Beethoven wrote his 32 piano sonatas between 1795 and 1822. Although originally not intended to be a meaningful whole, as a set they compose one of the most important collections of works in the history of music. Hans von Bülow called them "The New Testament" of the piano literature (Johann Sebastian Bach's "The Well-Tempered Clavier" being "The Old Testament").
Piano Sonatas Nos. 13 and 14 (Beethoven)
Ludwig van Beethoven's opus number 27 is a set of two piano sonatas. They were published separately in March 1802. Both sonatas are entitled "Sonata quasi una Fantasia", which roughly translated as sonatas in the style of a fantasia. The second sonata is one of the most famous piano works in the repertoire and often called the "Moonlight sonata", a contentious name not given by the composer himself. The first sonata remains far less performed than the second and the two sonatas are not commonly performed together.