The Beethoven Sonatas have been called the New Testament of the piano repertoire (the old being Bach’s Well-tempered Clavier).
Spanning the length of his compositional career, they illustrate Beethoven’s musical development, and show both the piano as an instrument and the piano sonata as a genre undergoing an extraordinary evolution.
Unsurprisingly, the most famous sonatas are those with nicknames, mostly invented by other people than the composer: Pathétique, the earliest of the "name" sonatas was a complete shock to the musical world with the unprecedented violence of its expression. Moonlight derives its name from the critic Ludwig Rellstab’s likening of the first movement to moonlight as reflected on the surface of Lake Lucerne. When asked about the meaning of the Sonata Op. 31 no 2, Beethoven replied: "Read Shakespeare’s Tempest".
The gigantic Hammerklavier Sonata, simply named after the German word for piano, occupies a pivotal position in Beethovens oevre: this work begins the transcendent spiritual odyssey of Beethoven’s late period.
The last three sonatas, with opus numbers 109-111 are some of his most forward-looking and experimental works.