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 flute music. Although this key was relatively unexplored during the Baroque and Classical periods, Franz Schubert used it quite frequently in his sets of écossaises, valses and so on, as well as entering it and even flatter keys in his sonatas, impromptus and the like. Ludwig van Beethoven, too, used this key extensively in his second piano concerto. D-flat major was used as the key for the slow movements of Joseph Haydn's Piano Sonata Hob XVI:46 in A-flat major, and Beethoven's "Appassionata Sonata". The flattened pitches of D-flat major correspond to the black keys of the piano, and there is