Franz Schubert wrote his Impromptus in 1827. These are eight pieces for solo piano, which were later published in two sets of four impromptus each, named Op. 90 and Op. posth. 142 (nowadays they are usually referred to by their Deutsch catalogue numbers, D. 899 and D. 935 respectively). These pieces are usually considered among the most popular examples of the impromptu genre, and they are usually found in recordings toghether with Schubert's Six Musical Moments. The Impromptus were allegedly inspired by the homonimous pieces of Jan Václav Voříšek.
The D. 935 has been compared to a sonata by some critics. While it is debatable that Schubert conceived this set of impromptus as a multi movement work, it is clear that he though of it as a continuation to the first set, as these were first numbered as nos. 4 to 8.