General Commentary

Composed in 1801. Sketches for the final movement can be found in the 'Sauer Sketchbook,' which the composer used from spring to autumn of the same year. Furthermore, similarities have been noted between a few measures of the musical idea in the first movement and sketches written in the 'Kafka Sketchbook,' used in 1793/94. The first edition was published in March 1802 by Giovanni Cappi in Vienna. Since Cappi initially used a common cover for Op. 27, No. 1 and No. 2 (the numbers 1 and 2 were initially added by hand), the numbering of the two works was reversed in many early published scores. No record of the premiere remains.

The work was dedicated to Countess Julie Guicciardi. She was a relative of the Brunswick family, who were close to Beethoven, and Beethoven, out of affection, taught Julie piano free of charge. Beethoven believed their affection was mutual, and she was mistakenly identified as the 'Immortal Beloved' in the Beethoven biography by the composer's secretary, Schindler.

The autograph fair copy remains in an almost complete state, but the first and last pages are missing. Therefore, the title notation written in the autograph score is unknown. However, the designation 'Sonata quasi una Fantasia' dates back to the first edition, and its authenticity from the composer is beyond doubt. This is interpreted as Beethoven's declaration of breaking from the traditional form of the piano sonata, writing a sonata with a free conception, like a fantasy. On the other hand, the common name 'Moonlight' originates from the poetic characterization of the first movement in L. Rellstab's literary work Theodor. A Musical Sketch from the 1830s. Furthermore, according to the 19th-century Beethoven scholar Wilhelm von Lenz (1809–1883), there was also a common name in Vienna, 'Gartenlaube Sonata' (Arbor Sonata), stemming from an anecdote that the composer improvised for the Countess in a garden.

It should be noted that while pedal markings are often used in the third movement in current published scores, pianos with pedals were not yet common in Vienna at the time this work was composed. Even on the Viennese Walter pianos favored by Beethoven, the damping mechanism was operated by a 'knee lever,' which was pushed up with the knee. In both Beethoven's autograph score and the first edition, the third movement of this work is indicated not by pedal markings but by the verbal instructions 'con sordino' and 'senza sordino'.

Movement-by-Movement Commentary

First Movement: Adagio sostenuto, 2/2 time, C-sharp minor

The opening movement of a piano sonata is generally a fast movement. Considering the title 'quasi una Fantasia,' placing an independent slow movement at the beginning, although there are precedents like Mozart's K. 331, can be regarded as the composer's deliberate choice to deviate from convention. Based on melody and harmony, the movement's form can be divided into an introduction (measures 1-5), A (measures 5-42), B (measures 23-42), A' (measures 42-60), and a postlude (measures 60-69). The entire movement is filled with Romantic musical language that invites the poetic interpretation from which 'Moonlight' derives (e.g., uniform triplets reminiscent of a barcarolle, and a lyrical melodic line with an introduction and postlude), and is considered a precursor to Mendelssohn's Songs Without Words.

Regarding the development and performance of the piano as an instrument, the handling of the damping mechanism is noteworthy. If one were to play this movement on a modern piano, following the instruction at the beginning of the movement, 'to play this entire piece [the concept of a movement is a later one] with the utmost delicacy, without sordino (damping device),' by keeping the dampers raised (i.e., holding down the right pedal), the reverberation would inevitably create ugly dissonances. However, the fortepianos of that time had a rapid decay of sound, and playing as instructed would likely produce an ineffable sound. It is also pointed out that the use of the damping mechanism throughout the movement reflects the history of damping devices operated by manual stops, predating pedals and knee levers.

Second Movement: Allegretto, 3/4 time, D-flat major

Compound ternary form. The choice of D-flat major as the main key, enharmonically related to the C-sharp minor of the outer movements, along with the type of the first movement, likely represents the composer's attempt to deviate from convention in key selection. Furthermore, the fact that the movement begins not with the root position of the tonic chord but with its first inversion, with F (the third) in the bass, also reveals an attempt to avoid extreme simplicity through harmonic ingenuity.

The opening theme of the main section consists of an alternation of two measures with contrasting articulations, legato and staccato, and a similarity to the second movement of Op. 26 has been noted here. The initial eight measures are immediately repeated with variation, and the syncopation in the melody here is common to the melodic structure of the trio section, contributing to the overall unity of the movement.

The beginning and end of the trio section are given a pastoral character by pedal points on the dominant or tonic. The harmonic stability of the tonic chord created by this is considered a measure to balance the main section, which begins with the tonic chord in its first inversion. After the repeat sign, where the pedal point disappears for the first time, the right hand also features a continuous succession of leaping figures in fifths or fourths, without stepwise motion, creating a contrast with the preceding and following sections.

Third Movement: Presto agitato, 4/4 time, C-sharp minor

Sonata form. From the beginning of the movement, the music rapidly builds in intensity through the restless motion of non-melodic arpeggios (referred to as A) and the gradually narrowing intervals of sf (sforzando) and harmonic changes. After a dominant pedal point, the transition section begins from measure 11. From measure 21, a melodic theme (referred to as B), contrasting with A, appears in the dominant key, G-sharp minor. However, the expected key stability of a secondary theme is low, and the bass quickly descends chromatically, moving away from G-sharp minor. From measure 43, where G-sharp minor becomes clear and stable again, the continuous sixteenth notes that had been present almost without interruption since the beginning of the movement disappear, and eighth notes become the standard rhythm; simultaneously, the texture changes to a contrasting succession of homophonic chords. The codetta (from measure 57) is based on B.

In the short development section, after themes A and B appear in the same order as in the exposition, a motive derived from the melody of measure 21 is varied over a dominant pedal point on G-sharp (the dominant of the movement's main key), harmonically preparing the recapitulation. The recapitulation concisely prepares the return of theme B in the tonic key by omitting the transition section.

The structure of the coda (from measure 159) corresponds to the development section in aspects such as themes A and B appearing in the same order as in the exposition, but improvisatory passages are inserted without warning between the previously stated themes. Here, one can point to a characteristic of the title 'quasi una Fantasia'. The rapid passages decrease in speed, and upon reaching the dominant with a stepwise ascent in the bass (a semitone ascent in the coda), corresponding to the end of the development section (measures 100-101, coda measures 188-189), the musical idea of the codetta reappears with the resolution to the tonic chord.