The last months of Franz Schubert's life were times of great physical illness matched with great musical creativity. But for most of his short life, Schubert was not anything if not prolific, as he wrote more than 1,500 works by the time of his death in 1828 at the age of 31. The final three piano sonatas were but a part of the works composed in his final months, and it wasn't until Schubert was ten years dead that they were published. Even then, it took many years for these last sonatas and most of Schubert's piano music to escape the neglect of the 19th century.
The Piano Sonata No. 19 In C Minor, D.958 is the first of this set of sonatas, and while all three of them have some similarities in structure, it is the C minor that is different in mood and character.
I. Allegro - As other authors have mentioned, the comparison with this sonata to those of Beethoven has been made many times. It does share the key of C minor with the powerful works of Beethoven in the same key. But Schubert's piano sonatas may have suffered in reputation by comparison to Beethoven's. What composer's wouldn't? But in the latter half of the 20th century, Schubert's sonatas were taken on their own terms, which is a good tactic to use for any music lover. This first movement begins with the starkness of a C minor chord, that shortly makes its way to a downward A-flat major scale, an example of Schubert's ear for combining differing harmonies. The C minor theme is repeated in a variation with a moving bass line that soon shifts keys to E-flat, relative major of C minor. Indeed, E-flat major is the key of the second theme which at first hearing, is calmer in nature, but upon the repetition this theme is varied by playing in octaves while the accompaniment is in triplets. This adds underlying tension to the music. Then there is a section that adds to the tension with shifting harmonies such as E-flat minor and A-flat minor. A final section of the exposition brings back the second theme, again with shifting harmonies. The exposition is repeated.
The key of A-flat major returns with the chord that leads off the development section, music that could have played a role in the development of Brahms, as the beginning sounds similar to the music of Brahms, who was an editor of some of Schubert's music. Most of the development deals with more shifting harmonies and a restless base.
The recapitulation begins with the first theme, along with variations in the next sections until the second theme is reached, which in this repetition is in C major, parallel key of C minor. The coda winds down the music with the second theme being in C minor, and the movement ends pianissimo.
II. Adagio - It was rare for Schubert to use the designation adagio for a movement, and it begins in A-flat major. The second theme shifts the key to A minor, and is much more agitated. The first theme is played again, with changes in harmony that change its benign mood into something darker. Once again, the second theme begins and darkens the mood. The first theme returns one last time and with changing keys, sounds somewhat deflated from before. It tries one last time to return to what it was before, but it quietly ends.
III. Menuetto: Allegro - Trio - Tranquility is in this movement more so than the preceding, but as incongruous as it may be to say, a disquietude is displayed with the bars of rest that interrupt the theme. The theme is in E-flat, but drifts into C minor and other keys. The key of A-flat major makes an appearance in the trio, with appearances of E-flat minor and other keys.
IV. Allegro - The final movement is in 6/8 time and is in the style of a tarantella. The music is in sonata form and begins in the home key of C minor for the first theme. The music drifts into other keys until a variant of this theme is played in C major. As this theme temporarily runs itself out, a transitional section in D-flat leads to the next theme in C-sharp minor. This theme is punctuated by a resounding rhythm in the left hand as the right hand crosses over it to play the theme. This theme continues to develop with modulations to A minor, E-flat major, E-flat minor, and leads to a third theme in E-flat major.
After this theme, a rest of two measures for the music to catch its breath brings a section in B major which leads to a development section that maintains the chromaticism of the sonata as it dances its way until a fermata over an eighth rest that signals the recapitulation.
The first theme is heard in the home key, the second theme changes key to B-flat minor, the third theme repeats in C major. A section in A-flat major leads to the coda with the first theme. Previous material is heard in different keys until the key of C minor takes off on two-note figures that outline the C minor triad (with a few accidentals that belong to G major) for 5 octaves while the bass plays a broken C minor chord (with a few accidentals that belong to G major). This 5-octave descent decreases the volume over its course until it reaches pianissimo. The music ends fortissimo the way it started; with a C minor chord.