General Remarks

An incomplete autograph manuscript, the initial draft of this work, has been preserved, bearing the inscription "May 1817" at its beginning.

Observing the overall movement structure of the sonata, the first movement is in A-flat major, followed by the second and third movements in E-flat major. Since the tonic key does not return at the end of the work, a question remains as to whether it should be considered a complete work in three movements. Various discussions have taken place in Schubert scholarship regarding this point. However, given that the copyist's manuscript, created during Schubert's lifetime, concludes with a complete third movement, and that the theme and form of the third movement are considered more appropriate for a finale than a middle movement, it is highly probable that the composer regarded the existing three movements as a single work.

Movement-by-Movement Analysis

Movement 1: Allegro moderato, A-flat major, 3/4 time

This movement is in sonata form. The first theme, presented in unison arpeggios, opens in A-flat major. The subsequent quiet transition section (from m. 11) leads to a half cadence on the double dominant (the dominant of the dominant), after which the second theme is gently presented in the dominant key (E-flat major) from m. 19, remaining quiet. When the second theme is repeated, it becomes more dynamic due to the accompaniment figures having shorter note values at mf.

What is noteworthy in the development section is that various motivic manipulations are carried out using material from the transition section, rather than from the two themes of the exposition. In the recapitulation, the opening theme returns in the tonic key, unlike the subdominant key used in the previous three piano sonatas. By recapitulating the transition section in D-flat major after a modulation at m. 71, the second theme is introduced in the tonic key.

Compared to previous piano sonatas, this movement is smaller in scale, and frequent modulations in the exposition are restrained. The compositional approach, employing motivic material and modulations only to the bare minimum, suggests as if Schubert was attempting to compose in a textbook-like form that would later be formalized.

Movement 2: Andante, E-flat major, 2/4 time

This movement is in ternary form (A-B-A'). Section A, beginning in E-flat major, primarily focuses on modulations to distant keys through sequences. A six-measure theme opens in E-flat major, and upon its repetition with voice exchange between the left and right hands, it leads to a half cadence on a B-flat major triad. This triad leads to the presentation of a theme in the parallel minor, E-flat minor, and further modulates to its relative major, G-flat major (m. 17). From here, it proceeds through F-sharp minor (reinterpreted enharmonically) to D major, and then through a modulation to B-flat major using a mediant relationship, finally concluding with a perfect cadence in the tonic key at the end of Section A (m. 33).

Led by a reappearing E-flat major cadence, Section B suddenly opens in E-flat minor (m. 38). Section B contrasts with the main section in terms of its motion, characterized by 32nd-note passages, and its dynamics. This Section B is also in ternary form, encompassing quiet middle sections in G-flat major and D-flat major.

Subsequently, the opening theme returns at m. 71, marking the recapitulation of Section A, but this is not merely a simple return of Section A. Not only does the opening theme return an octave lower, but the initial Section A and the recapitulated A' section also differ in their tonal plan, modulating to C-flat major and A-flat major/A-flat minor. This demonstrates Schubert's formal experimentation, avoiding mere repetition while using the same theme.

Movement 3: Allegro, E-flat major, 6/8 time

A bright final movement written in sonata form. The first theme group of the exposition is in E-flat major, consisting of a light, quiet section (mm. 1-14) and a dynamic, loud section with 16th-note accompaniment (mm. 14-20). Once the first theme group reaches a half cadence, the second theme group is presented from m. 21 in the dominant key, B-flat major. Here, the same melody is played twice, accompanied by eighth notes and then by sixteenth notes. The exposition closes in B-flat major, interspersed with a sudden modulation to D-flat major (m. 37).

The development section opens in F minor, with this B-flat serving as the seventh of the dominant seventh chord. It consists of a first half supported by 16th-note accompaniment and a second half primarily featuring eighth notes; both sections undergo rapid modulations through extensive use of sequences.

In the recapitulation (m. 86), both theme groups from the exposition return in the tonic key. Just as the second theme group in B-flat major deviated to D-flat major in the exposition, so too in the recapitulation, at the same point in the second theme group, it deviates from E-flat major to G-flat major. The technique observed here, of modulating to a mediant key in both the exposition and the recapitulation, can be interpreted as a nascent form of Schubert's later sonata forms, which present three themes in three different keys.