환상곡 다단조, K. 475 (Fantasia in C minor, K.475)

Fantasia No. 4 in C minor, K. 475 is a composition for solo piano composed by Wolfgang Amadeus Mozart in Vienna on 20 May 1785. It was published as Opus 11 in December 1785, together with the Sonata in C minor, K. 457, the only one of Mozart's piano sonatas to be published together with a work of a different genre. 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♭ 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 key of C minor. Most of the music is written with no sharps or flats in the key signature and uses accidentals—only the fourth section, in B♭ major, is given a key signature. The autograph manuscript of this composition was auctioned by Sotheby's on 21 November 1990, and is now preserved in the International Mozarteum Foundation. The Austrian composer Ignaz von Seyfried combined this work with the Sonata in C minor, K. 457, and produced a four-movement arrangement for orchestra, the "Grande Fantaisie" in C minor. Tchaikovsky arranged the Andantino section to a vocal quartet with piano by the name "Night" ("Ночь").