Piano Sonata in C major, D 840 (Schubert)

Franz Schubert's Piano Sonata in C major, D. 840, nicknamed "Reliquie" upon its first publication in 1861 in the mistaken belief that it had been Schubert's last work, was written in April 1825, whilst the composer was also working on the A minor sonata, D. 845 in tandem. Schubert abandoned the C major sonata, and only the first two movements were fully completed, with the trio section of the third movement also written in full. The minuet section of the third movement is incomplete and contains unusual harmonic changes, which suggests it was there Schubert had become disillusioned and abandoned the movement and later the sonata. The final fourth movement is also incomplete, ending abruptly after 272 measures.
The fragments of the sonata survived in Schubert's manuscripts, and later the work was collected and published in its incomplete form in 1861.
Movements.
I. Moderato
C major, 4/4 time, sonata form
"Duration approximately 15 to 18 minutes"
II. Andante
C minor, 6/8 time, five-part rondo form
"Duration approximately 10 minutes"
III. Menuetto: Allegretto – Trio
A-flat major, 3/4 time, incomplete ternary form. Fragment (ends at measure 80 after the main theme returns in the B part of the menuetto)
Very unusually, the opening theme is immediately repeated, slightly embellished, in A major, and the reprise also begins in this key. Presumably the minuet would have then returned to A-flat major. The trio is in the parallel minor, notated enharmonically as G-sharp minor.
IV. Rondo: Allegro
C major. Fragment (ends 32 measures after the development starts)
Even in this truncated form, the sonata takes approximately 30 to 35 minutes to perform.
Structure.
Ernst Krenek outlined the structure of each of the work's four movements in notes that he contributed to a recording by Ray Lev in 1947. Krenek elaborates on how he composed a completion, included in the recording, for the unfinished movements. According to Krenek:
Completions.
Given its large scope and the extent of material that Schubert left for the incomplete movements, this sonata has inspired various composers and performers to undertake completions. Some of their efforts, particularly those penned by performers, have appeared on records. Among them are the following: