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
E-flat major in E-flat major. Mahler's vast and heroic Eighth Symphony is in E-flat and his Second Symphony also ends in the key. This is not to say that, in the Classical period, E-flat major was only for bombastic music with brass. "E-flat was the key [Joseph] Haydn chose most often for [string] quartets, ten times in all, and in every other case he wrote the slow movement in the dominant, B-flat." Or "when composing church music and operatic music in E-flat major, [Joseph] Haydn often substituted cors anglais for oboes in this period", and also in the Symphony No. 22 in