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D-flat major is a major scale based on D♭, consisting of the pitches D♭, E♭, F, G♭, A♭, B♭ and C. Its key signature has five flats. It is enharmonically equivalent to C-sharp major.
The D-flat major scale is:
Its relative minor is B-flat minor. Its parallel minor, D-flat minor, is usually replaced by C-sharp minor, since D-flat minor features a B in its key signature making it impractical to use. C-sharp major, the enharmonic equivalent to D-flat major, has a similar problem as it contains seven sharps. Therefore, D-flat major is often used as the parallel major for C-sharp minor..
For example, in his Prelude No. 15 in D-flat major , Frédéric Chopin switches from D-flat major to C-sharp minor for the middle section in the parallel minor, while in his Fantaisie-Impromptu and Scherzo No. 3, primarily in C-sharp minor, he switches to D-flat major for the middle section for the opposite reason. Ferdinand Ries' third concerto likewise switches to D-flat major for a while for the return of the second theme in the first movement. Claude Debussy also switches from D-flat major to C-sharp minor in the significant section in his famous "Clair de lune". Antonín Dvořák's New World Symphony likewise switches to C-sharp minor for a while for the significant section in the slow movement.