"Rare key in which a section of Chopin's ""Polonaise Fantaisie"" is written" crossword clue

Let me guess, you have been playing a crossword game and got stuck on the clue "Rare key in which a section of Chopin's ""Polonaise Fantaisie"" is written". Well, you have come to the right place to find the answer to this clue.

A S H A R P M I N O R