The Sonata in C minor, D. 958 marks the first works of the kind since Beethoven’s death the previous year, and Schubert seems at last to have felt free to challenge the great composer on his own ground. The work was written three months before Schubert’s death and comprises 4 movements.
In the Allegro, the exposition shifts from the tonic to the relative major (E-flat major), touching midway upon its parallel minor (E-flat minor), all in accordance with Classical practice. The development section is highly chromatic, and is texturally and melodically distinct from the exposition.
The recapitulation is once again traditional, staying in the tonic and stressing subdominant tonalities (D-flat, the lowered second degree – in the first theme). The coda returns to the material of the development section, but with stable tonality.
The Adagio is written in A-flat major, and has the A–B–A–B–A form. The unorthodox, chromatic harmonic structure of this movement is generated from a short progression that appears towards the end of the A section, leading to a plagal cadence in the subdominant key (D-flat), chromatically colored with its own minor subdominant chord (G-flat minor). This leads to the haunted atmosphere of the B section, which is full of chromatic modulations and ‘frightening’ sforzandos. In the second appearance of the A and B sections, almost the entire music is shifted a semitone up. The ‘kernel’ progression returns transformed at the end of the movement, with even subtler chromatic coloration and harsher modulations, leading from A-flat minor to C major. Throughout the entire movement, brisk modulations of a rising or falling semitone predominate.
The third movement is a somber one, quite distinct from the typical atmosphere of dance movements. It is relatively conservative in its key scheme, moving to the relative major key and back to the tonic. In the B section, a sequence of hemiolas is interrupted by a dramatic interpolation in A-flat major. The second A section is a transformation of the first, interrupted every four bars by a silent bar, creating a mysterious atmosphere. The trio is in A-flat major, ternary form.
The last movement is written in 6/8 and in tarantella style, and is characterised by a relentless galloping rhythm. It employs the three-key exposition, a recurrent element in Schubert’s style. The first theme shifts from C minor to C major – another Schubertian feature, and contains many allusions to D-flat major, which eventually becomes the key of the second theme. After a series of modulations, the exposition ends in the traditional relative major, E-flat. The development section begins in C-flat with a new theme, derived from the last bars of the exposition. Later on, additional material from the exposition is developed, gradually building up towards a climax. The recapitulation is also written in three keys, this time the second theme in B-flat minor and the closing section in the traditional tonic. The coda begins with a long anticipatory passage which stresses A-flat, the submediant, and then reintroduces the first theme, gradually building up tension towards the fortissimo ending.
III. Menuetto: Allegro – Trio