Beethoven takes a new step with this Sonata Op. 26. This begins with the deliberate avoidance of a main sonata-form movement, instead structuring the entire sonata with variations and character pieces. However, this musical structure is likely composed with Mozart's Sonata in A major, K. 331 as a model, rather than being Beethoven's entirely original idea.

The fact that the opening movement is composed as a set of variations, and the subsequent movements are in dance form (minuet in Mozart) and march form (Turkish March in Mozart), cannot be a mere coincidence.

Nevertheless, Beethoven's originality is evident in his introduction of a scherzo as the dance form and his conclusion of the work with a toccata-like finale. The finale, in particular, with its improvisatory character, is uncomfortable within the traditional framework of a "sonata," but it can be seen as having a common thread with Chopin's later Piano Sonata No. 2, where the finale is also concluded with toccata-like, improvisatory passages.

It is worth noting that around 1800-01, when this work is presumed to have been composed, Beethoven completed works such as Symphony No. 1, Op. 21, and String Quartets, Op. 18. This was a period full of creative drive, and one can observe Beethoven's courageous approach to the tradition of the sonata.

First Movement: A-flat Major, 3/8 time, Variation Form

Consists of a 34-measure theme without repeat signs, followed by five variations. This long theme is structured in three parts: an opening 8-measure phrase and its repetition (up to m. 16), a transitional 10-measure phrase where the anacrusis is emphasized by sforzandos (up to m. 26), and finally, a return of the opening idea (up to m. 34) leading to a perfect cadence.

In the subsequent five variations, the harmonic progression of the theme is largely preserved, with each variation presenting a distinctive figural transformation. The third variation modulates to the parallel minor, A-flat minor.

Second Movement: A-flat Major, 3/4 time, Scherzo

The scherzo theme, ascending stepwise from A-flat to E-flat, immediately surprises by incorporating D natural, a note not inherent to the A-flat major scale. While this stepwise progression might suggest a Lydian mode, this 4-measure motive concludes in E-flat major. Its immediate repetition a fourth higher (from D-flat) to conclude in A-flat major reveals that the opening began in the dominant key. Such surprising openings for the listener are also seen at the beginning of Symphony No. 1, composed around the same period. This compositional approach, which can be interpreted as both "playful" and "ambitious," is a characteristic aspect of Beethoven's style during this period.

After the presentation and confirmation of the 16-measure scherzo theme, the main section (A-flat major) begins, treating the theme in a developmental manner. Note that the initial 16 measures are omitted during the da capo.

The trio is in the subdominant key of D-flat major. While the opening was introduced with a dominant-to-tonic relationship, the tonal relationship from the trio to the main section is reversed to subdominant-to-tonic.

Third Movement: A-flat minor, 4/4 time, Funeral March

A three-part funeral march, characterized by an anacrusis and dotted rhythms, where a 4-measure idea and its development return after an intervening middle section.

In the main section, there is a modulation to B minor (enharmonically reinterpreted as the parallel minor of C-flat major, the relative major), then to its parallel major, D major. From there, it converges to the tonic via a double dominant of A-flat minor, using D natural as a common tone. The middle section is in the parallel major, A-flat major.

Fourth Movement: A-flat Major, 2/4 time

The toccata-like finale, due to its figural characteristics, its limited use of tonality compared to the tonal development in the second and third movements, and its irregular phrase structure in contrast to the persistent adherence to 4- and 8-measure phrase units in the preceding three movements, appears to have originated from an improvisation or something very close to it.