Schubert - Four Impromptus D. 935 (Op. posth. 142)

The word impromptu by definition implies something that is spontaneous, improvised. That definition does not really imply in music, for the impromptus as written by Schubert and other composers are hardly improvisations. They are well-crafted short pieces for the piano that have a definite structure.

Schubert wrote eight impromptus, but he was not the first to use the term. The first known use of the word for published musical works was by the Czech composer and pianist Jan Václav Voříšek in his opus 7 set of six piano pieces in 1822.  Voříšek and Schubert knew each other in Vienna, and Schubert may have been inspired by Voříšek's opus 7 set.

All eight of Schubert's impromptus were written in 1827, a year before the composer died. Two of them were published shortly after they were written, and Schubert's publisher suggested calling them impromptus. The other six were published sporadically after his death. The complete set of eight was published in 1857, thirty years after they were written, and are now considered to be in two sets of four each; D.899 and D.935. The four pieces of D.935 are discussed below:

1) F Minor - This impromptu can be broken down into 3 major sections. The first section is a group of themes that begins with one in F minor:

The second section is in A-flat major and is of a decidedly more lyrical nature. The third and longer section enters in A-flat minor with alternating statements in the treble and bass with a continuing accompaniment. This section modulates to the major before sections 1 and 2 are repeated. The third section is also repeated, this time in the home key. The first section makes one more brief appearance to end the piece.

2) A-flat Major -  Written in the same form as a minuet with the opening in A-flat major:

The trio section begins in D-flat major in triplets. The key changes to D-flat minor before the opening material returns.

3) B-flat Major, Theme and Variations -  A theme with 5 variations:

Variation I has the theme repeated in a dotted rhythm at the top of the right hand with an accompaniment also played in the right hand and left hand.
Variation II has the theme ornamented.
Variation III is in B-flat minor. Somber chords in the left hand accompany the moody minor variation of the theme.
Variation IV is in G-flat major with the theme carried in the left hand at the start. The theme alternates between hands.
Variation V has the theme return to the home key of B-flat major as the theme is delicately outlined with runs in the right hand. A short coda ends the piece.

4) F minor, Tempo Scherzando - Written in F minor and in 3/8 time. As Schubert was wont to do in his later works the form (which is ternary) is expanded with many different sections and themes within the parts as well as going far afield from the home key within the piece. The first part has 4 different sections and begins with the scherzo theme:

The second part has two sections and functions as a trio. The first part is repeated after the trio. A long coda section picks up the tempo towards the end and the piece ends with a thundering F minor scale the length of the keyboard.