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 Beethoven's (hypothetical) 10th symphony is in the key of E-flat major. But even before Beethoven, Francesco Galeazzi identified E-flat major as "a heroic key, extremely majestic, grave and serious: in all these features it is superior to that of C." Three of Mozart's completed horn concertos and Joseph Haydn's famous Trumpet Concerto are in E-flat major and so is Anton Bruckner's Fourth Symphony with its prominent horn theme in the first movement. Another famous heroic piece in the key of E-flat major is Richard Strauss's "A Hero's Life". The heroic theme from the Jupiter movement of Holst's "The Planets" is