The Fantasy of Schubert is considered to be one of the most difficult pieces in the whole classical repertoire, for both instruments. The piece is the biggest in the rather small amount of pieces of Schubert for these two instruments but can be seen as one of the greatest works a duo can play.
The Fantasy was composed in December 1827 and did not go into print until 1850 when Anton Diabelli published many posthumous pieces of Schubert. This major piece was premiered in a private concert in January 1828 by Josef Slawik, a virtuoso violinist ,and Karl Maria von Bocklet at the piano.
There are quite some changes between the Manuscript and the first edition. Most of them are simplifications in the virtuoso violin part. It is not sure who made those changes and if they were upon agreement of Schubert himself.
The themes come back throughout the movements and the movements itself are connected which creates the effect of a one-movement form.
The first movement can be seen as a major introduction to the second movement. It is written in an Andante-tempo and has the typical accompaniment of tremolos throughout the movement. It is an extremely hard part for both instruments, for the equality in the part of the pianist and the rather long lines of the violin.
The second movement has, like in the sonatinas Op.137, the typical accompaniment of repeated rhythmical patterns. The main line is introduced by the violin and the piano repeats, while the violinist repeats the counterpart which initially the right hand of the pianist was playing. With the conclusion of that part, the theme starts again which now becomes canonic. A more playful second part to contrast this theme is introduced and has a major role in this movement. The whole part, with both themes, does get repeated, after an interesting bridge. This movement is very intertwined and both instruments have an equal role in the music. Schubert does not end the movement in a typical way and writes in the last bar a Fermata sign without a closing barline.
The third movement is written in A-flat major, and is written in a variation form. Both instruments get their share of virtuosity but are not composed in such a way to show off as became a custom after Schubert's time in the 19th century. It is extremely difficult for both instruments separately and the composition style, where for example all the 32nd notes are written in both instruments, make this movement even more complex. The movement ends again with an open ending and a fermate sign, like the second movement, and brings us back to the introduction (first) movement. This part goes straight into the fourth, and final, movement.
The fourth movement is an Allegro Vivace which gets the introduction by the piano. The violin enters and plays the theme with the piano. This doubling gives a more powerful effect. This melody gets often repeated throughout the piece and has an extremely difficult part for the violin. The Allegretto brings us to the Presto Coda which completes the Fantasy in a grand style.