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)
Beethoven later reused material from the C major quartet for two of his early Piano Sonatas: No. 1 and No. 3. In Beethoven's original manuscript, the work in C major comes first, followed by E-flat major and D major. When the quartets were published after his death by Artaria in Vienna, there were in a different order: E-flat major, D major and C major.