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 Quartets (Beethoven)
The Piano Quartets, WoO 36, by Ludwig van Beethoven are a set of three piano quartets, completed in 1785 when the composer was aged 15. They are scored for piano, violin, viola and cello. He composed a quartet in C major, another in E-flat major, and a third in D major. They were first published posthumously in 1828, however numbered in a different order: Piano Quartet No. 1 in E-flat major, Piano Quartet No. 2 in D major, and Piano Quartet No. 3 in C major.