Movement 4: Allegretto, A-flat minor, 3/4 time

This movement adopts a ternary form (main section – trio section – main section), with each section constructed using various chords.

The main section begins in A-flat minor, characterized by right-hand arpeggios and a left-hand rhythm emphasizing the second beat. After four bars of active movement alternate with two bars of quarter notes that halt the motion, a sequence of eight bars of quarter-note chords follows, leading to a sudden shift to A-flat major. Such abrupt changes between major and minor keys were a favored technique of Schubert. In A-flat major, the quarter-note phrases disappear, and the arpeggios, which were in two-bar units at the beginning, contract to one-bar units, creating a sense of urgency. Building upon this, a melodic theme first appears in the lower voice (m. 47), gradually building to a dissonance (m. 68). As it subsides, the aforementioned theme is played in the upper voice accompanied by triplet arpeggios (m. 72), and sixteenth-note arpeggios return, closing the main section.

The Trio section reinterprets A-flat as G-sharp, becoming C-sharp minor. Here, the melody is supported not by arpeggios, but by repeated chords. The Trio section also adopts a ternary form, but the main theme returns in the parallel major (m. 139), and a major-minor shift occurs.

When the main section returns, there is no coda, and it concludes majestically with a two-chord cadence, remaining in A-flat major. Unlike the first movement, it ends definitively in a major key.