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").
Cello Sonata No. 3 (Beethoven)
In the course of his life Beethoven composed five sonatas for cello and piano. The Op. 69 was the first he had written since his Op. 5 over a decade earlier. Mark Kaplan writes: "In general, the writing in op. 69 is thinner than in the early cello sonatas ... greater compositional technique allowed Beethoven the possibility of using fewer notes with confidence." The contemporary cellist Steven Isserlis describes it as the first cello sonata in history to give the two instruments equal importance.