[Liner notes adapted from wikimedia.org and published here subject to a Creative Commons license.]
Ludwig van Beethoven's Piano Sonata No. 23 in F minor, Op. 57 (colloquially known as the Appassionata) is a piano sonata. Among the three famous piano sonatas of his middle period (the others being the Waldstein, Op. 53 and Les Adieux, Op. 81a). It was composed during 1804 and 1805, and perhaps 1806, and was dedicated to Count Franz von Brunswick. The first edition was published in February 1807 in Vienna.
Unlike the early Sonata No. 8, Pathétique, the Appassionata was not named during the composer's lifetime, but was so labeled in 1838 by the publisher of a four-hand arrangement of the work.
The Appassionata was considered by Beethoven to be his most tempestuous piano sonata until the twenty-ninth piano sonata known as the Hammerklavier being described as a "brilliantly executed display of emotion and music". 1803 was the year Beethoven came to grips with the irreversibility of his progressively deteriorating deafness.
I. Allegro assai
A sonata-allegro form in 12/8 time, the first movement moves quickly through startling changes in tone and dynamics, and is characterized by an economic use of themes.
The main theme, in octaves, is quiet and ominous. It consists of a down-and-up arpeggio in dotted rhythm that cadences on the "tonicized" dominant, immediately repeated a semitone higher (in G flat). This use of the Neapolitan chord (e.g. the flatted supertonic) is an important structural element in the work, also being the basis of the main theme of the finale. The rhythm of the theme is based on the English folk song On the Banks of Allen Water.
The second subject is a direct quotation of the first two lines of the folk song, conformed to fit the 12/8 time (the folk song is in 3/4). As in Beethoven's Waldstein sonata, the coda is unusually long, containing quasi-improvisational arpeggios which span most of the [early 19th-century] piano's range. The choice of F-minor becomes very clear when one realizes that this movement makes frequent use of the deep, dark tone of the lowest F on the piano, which was the lowest note available to Beethoven at the time.
II. Andante con moto
The second movement consists of a set of variations in D flat major following a theme as remarkable for its sophistication as its simplicity. Its main sixteen bars are founded only on the most common chords in western music with each stanza reflecting structural consistency with four- and two-bar phrases all ending on the tonic. A summary of the four variations follows:
Var. I: similar to the original theme, with the left hand playing on the off-beats.
Var. II: an embellishment of the theme in sixteenth notes.
Var. III: a rapid embellishment in thirty-second notes with a double variation as the hands switch parts.
Var. IV: a reprise of the original theme without repeats and with the phrases displaced in register.
The fourth variation cadences deceptively on a soft diminished-7th chord, followed by a much louder diminished-7th that serves as a transition to the finale.
III. Allegro ma non troppo - Presto
Follows sonata-allegro form with almost perpetual motion, and has much in common with the first movement including extensive use of the Neapolitan sixth chord and several written-out cadenzas. The movement climaxes with a faster coda introducing a new theme which in turn leads into a bravura extended final cadence in F minor.