Debussy's Prelude VIII
This prelude is a good example of how Debussy uses chords to give color to his music.
The first time that we hear this theme, it appears almost without any accompaniment. Only a plagal cadence to Gb Major appears at the end of the phrase.
The next time two dominant seventh chords in 3rd inversion are used. The phrase ends with a V-I cadence to Gb Major.
In measures 24 and 25 the theme appears with some variations. The chords used are formed with notes of the pentatonic scale. Note that intervals other that 3rds are used in these chords.
Finally, in measures 28 - 30 the melody appears over a Cb major chord: