Sonata in C minor, D. 958

I. Allegro

The opening is dramatic, with a fully voiced, forte C-minor chord. The voice leading of this passage outlines a chromatic ascent to A♭ – this will be the first instance of a remarkable degree of chromaticism in the sonata as a whole. The most salient feature of the first theme is the sudden modulatory digression to A♭ major, established by a rushing downward scale initiated by the final achievement of this key in the ascending voice of the minor theme. The exposition shifts from the tonic to the relative major (E♭major), touching midway upon its parallel minor (E♭ minor), all in accordance with Classical practice. This second theme, a hymn-like E♭ major melody in four-part harmony, greatly contrasts with the first, though its melodic contour is prefigured in the sudden A♭ major departure. Both themes progress somewhat in the style of variations and are structured with irregular phrase lengths.

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♭, the lowered second degree – in the first theme). The coda returns to the material of the development section but with stable tonality, dying out in a dark series of cadences in low register.

II. Adagio

The second movement is in A♭ major, ABABA form. Nostalgic in its traditional Classical character (one of the few instrumental Adagios Schubert wrote), the opening theme of this movement is an elegant, touching melody that eventually undergoes remarkable tonal and cadential treatment, undermining the peaceful setting. Charles Fisk has pointed out that the voice leading of the first phrase, 1–7–1–2–3–4–3, is based on the initial A♭ digression in the beginning of the Allegro. 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 cadencein the subdominant key (D♭), chromatically colored with its own minor subdominant chord (G♭ minor). The importance of this progression and of D♭ in general is emphasized by its quotation in a climax of the finale's exposition. This diversion of the main theme's expected cadence leads to the haunted atmosphere of the B section, which is full of chromatic modulations and startling sforzandos.

In the second appearance of the A and B sections, almost the entire music is shifted a semitone up, further cementing the importance of the ascending minor second in the sonata as a whole. The focal plagal progression returns transformed at the end of the movement, with even subtler chromatic coloration and more distant modulations, touching on C major, before the piece finally ends in the tonic, the theme now weakened and given an illusory quality due to the evasion of cadences, free modulation, and tendency toward digression into troubled minor passages.

III. Menuetto: Allegro – Trio

The third movement is somber, 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♭ major, referencing the departure to this key in the opening of the Allegro with the added minor sixth. 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♭major, ternary form, with a B section beginning in E♭ major colored by its own minor sixth and modulating to G♭ major via the parallel minor.

IV. Allegro

This movement is written in 6/8 and in tarantella style and is characterised by a relentless galloping rhythm calling on demanding pianistic effects with frequent hand-crossing and leaps across registers. 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♭major, which finally becomes established in a climactic reference to the Adagio's characteristic plagal cadence. The second theme, proceeding with the enharmonic parallel minor of this cadence (C♯ minor), further develops the cadence in its alternation of tonic and subdominant tonalities. After a series of modulations, the exposition ends in the traditional relative major, E♭.

The development section begins in C♭ 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; the first theme is drastically shortened, and this time the second theme veers to B♭ minor, the result being that the closing section appears in the traditional tonic.

The coda begins with a long anticipatory passage which stresses A♭, the submediant, and then reintroduces the first theme, restoring most of the music omitted from its reprise. This last passage is characterized by sweeping arpeggios with violent dynamic contrasts – a series of subito fortissimo decaying to piano, following the rise and fall of the melody. On the last iteration, the melody hits triple forteat the zenith of its register and then plunges four octaves in a descending arpeggio, marked poco a poco diminuendo al pianissimo. An emphatic cadence then concludes the piece.

Read more: https://en.wikipedia.org/wiki/Schubert%27s_last_sonatas