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 major, although they usually notate this with accidentals in some other key signature, seldom a 7-flat key signature: for example: C major is used for Benjamin Britten's "Interlude" in C major for harp, several of Max Reger's Canons in All Major and Minor Keys (Book 1 Nos. 62 and 63, and Book 2 No. 48), and No. 29 from the "Thirty Preludes in All Major and Minor Keys" by Christian Heinrich Rinck. In some scores, the C major key signature in the bass clef is written with the flat for the F on the second line from the top. This