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").
Ludwig van Beethoven
In May 1799, he taught piano to the daughters of Hungarian Countess Anna Brunsvik. During this time, he fell in love with the younger daughter Josephine who has therefore been identified as one of the more likely candidates for the addressee of his letter to the "Immortal Beloved" (in 1812). Shortly after these lessons, Josephine was married to Count Josef Deym. Beethoven was a regular visitor at their house, continuing to teach Josephine, and playing at parties and concerts. Her marriage was by all accounts happy (despite initial financial problems), and the couple had four children. Her relationship with Beethoven intensified after Deym died suddenly in 1804.
He also had a few other students. From 1801 to 1805, he tutored Ferdinand Ries, who went on to become a composer and later wrote "Beethoven remembered", a book about their encounters. The young Carl Czerny studied with Beethoven from 1801 to 1803. Czerny went on to become a renowned music teacher himself, instructing Franz Liszt, and on 11 February 1812 gave the Vienna premiere of Beethoven's fifth piano concerto (the "Emperor").