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").
Arpeggione Sonata
The Sonata in A minor for Arpeggione and Piano, D. 821, was written by Franz Schubert in Vienna in November 1824. The sonata is the only substantial composition for the arpeggione (which was essentially a bowed guitar) which remains extant today. The sonata was composed in November 1824, about a month after he had returned to Vienna from his second stay in Zseliz.