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
C-flat major and is now playing in B major, marked with the necessary sharps and naturals as accidentals. This use of C major in harp parts when the rest of the orchestra is playing in B major is not exceptional: it is standard practice in orchestral music written in B major for harp parts to be notated in C major. In Arnold Bax's symphonic poem "Tintagel", the key is B major and again the harp part is always notated in C major; but in this case the harp's key signature contains only 6 flats, and the necessary Fs are notated with accidentals.