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").
Beethoven's musical style
Beethoven's musical output has traditionally been divided into three periods, a classification that dates to the first years after the composer's death in 1827 and was formalised with the publication of Wilhelm von Lenz's influential work "Beethoven et ses trois styles" (Beethoven and his Three Styles). Lenz proposed that Beethoven's creative output be marked by three periods of distinct stylistic personality and he identified specific compositions as milestones for each period. In Lenz's work, the first period opens with Beethoven's Trio set, Opus 1 and culminates with the performances in 1800 of his first symphony and Septet. The second period spans the period from the publication of his Moonlight Sonata to the Piano Sonata in E minor, Op. 90 in 1814. The last period covers Beethoven's mature works to his death in 1827.