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 much significant piano music written in this key. Pyotr Ilyich Tchaikovsky's Piano Concerto No. 1 is written in B-flat minor, but the famous opening theme is in D-flat major. Tchaikovsky composed the second movement of Piano Concerto No. 1 also in D-flat. Sergei Rachmaninoff composed the famous 18th variation of his "Rhapsody on a Theme of Paganini" in this key, perhaps emphasizing the generally held view that D-flat major is the most romantically flavoured of the major keys; and his friend Nikolai Medtner similarly chose it for the sensually romantic "big tune" in the last movement of his Piano Concerto