The Fantasy in C minor, K. 475 is a piece of music for solo piano composed by Wolfgang Amadeus Mozart in 1785. It was published in the same year with the Sonata K. 457 by the publishing firm Artaria, Mozart’s main Viennese publisher. Starting in the key of C minor, the piece is marked Adagio but then, after a section in D major, moves into an allegro section which goes from A minor to G minor, F major, and then F minor. It then moves into a fourth section in B-flat major marked Andantino and then moves to a più allegro section starting in G minor and modulating through many keys before the opening theme returns in the original tonic key of C minor--the remainder of the piece is, for the first time, grounded in this key, in which it comes to a very firm end. Due to its sometimes surprising key changes, most of the music is written with no sharps or flats in the key signature and uses accidentals--only the fourth section, in a very solid B-flat major, is given a key signature. The music, like Mozart's other fantasies, is thought of as quite technically demanding.
