G-flat major Rondo-Finale of his Seventh Symphony. Mahler's Tenth Symphony was composed in the enharmonic key of F-sharp major. This key is more often found in piano music, as the use of all five black keys allows an easier conformity to the player's hands, despite the numerous flats. Austrian composer Franz Schubert chose this key for his third impromptu from his first collection of impromptus (1827). Polish composer Frédéric Chopin wrote two études in the key of G-flat major: Étude Op. 10, No. 5 "Black Key" and Étude Op. 25, No. 9 "Butterfly". French composer Claude Debussy used this key for one
D-flat major its enharmonic, with seven sharps, has a similar problem. Therefore, D-flat major is often used as the parallel major for C-sharp minor. (The same enharmonic situation occurs with the keys of A-flat major and G-sharp minor). For example, in his Prelude No. 15 in D-flat major ("Raindrop"), Frédéric Chopin switches from D-flat major to C-sharp minor for the middle section in the parallel minor, while in his "Fantaisie-Impromptu" and Scherzo No. 3, primarily in C-sharp minor, he switches to D-flat major for the middle section for the opposite reason. Ferdinand Ries' third concerto likewise switches to D-flat major for a