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").
Yellowhammer
Beethoven's student, Carl Czerny, and biographer Anton Schindler, both suggested that the composer got the idea for the first four notes of his 5th symphony from the yellowhammer's call, although it is more likely that the opening of the 4th Piano Concerto was actually the work in question. Beethoven also used the yellowhammer theme in two piano sonatas, no. 21 in C major (the "Waldstein", Op.53) and No. 23 in F minor (the "Appassionata", Op.57).