Frédéric Chopin's Fantaisie-Impromptu in C-sharp minor is a solo piano composition. It is one of his best-known pieces. It was composed in 1834 and was published by Julian Fontana after though even though Chopin asked him not to do so.
The structure of the piece is in A B A Coda form. Some aspects of this piece are similar to Beethoven's "Moonlight" Sonata. The opening tempo is allegro agitato. It changes to largo for the two bars after the 'A' section. The tempo for most of the 'B' section is moderato cantabile. Finally, after the 'B' section, it changes to presto. The piece on a C-sharp major rolled chord.