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").
Violin sonata
Beethoven wrote ten violin sonatas throughout his composing career. His sonatas matured in both style and complexity; the Ninth (Kreutzer) Sonata is a work of extreme contrasts. A rendition typically lasts forty minutes and is very demanding on both players.