Fantasy No. 4 in C minor, K. 475 (Fantasie in German) is a piece of music for solo piano composed by Wolfgang Amadeus Mozart in Vienna on May 20, 1785. It was published in December 1785 together with the Sonata in C minor, K. 457, as Opus 11 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. Performed by Mitsuko Uchida.