Dominant seventh, ninth, eleventh and thirteenth chords are
common in Debussy's Preludes. Their use is indicative of the functional
disintegration in harmony. The clear-cut harmonic shapes of classical
tonality became gradually obscurred. With the use of these chords
remaining unresolved, and the frequency of intervals such as the second
and. seventh appearing in these chords, a new concept of dissonance arose.
These dissonant tones occur in such a way as to reduce their "shock"
value to a minimum and heighten their "sound" value to a maximum.
These chords exist purely as combinations of sounds for their sonorous
effect. Examples 15 and 16 illustrate the use of dominant ninth and
eleventh chords.