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 sonatas (Boulez)
Boulez's First Piano Sonata, completed in 1946, has two movements. It was his first twelve-tone serial work (together with his Sonatine for flute and piano), and he originally intended to dedicate it to René Leibowitz, but their friendship ended when Leibowitz tried to make "corrections" to the score (, quoted without a page reference in ).