Extended Harmony

The use of ninths, elevenths and thirteen chords was common in Debussy's music. Follows some examples of these types of chords in this prelude.

Measure 9, Db with 7th, 9th and 11th:

This chord has a dominant of Gb function.

Measure 12, Gb with 9th, 11th y 13th:

Measure 17, Ab minor with 9th and Db minor with 9th:

Measure 18, Bb major with 7th, 9th y 11th:

This chord has a dominant of Eb function.

Additional resources about extended chords:

Ninth chords, teoría's Online Reference
Eleventh and Thirteenth chords, teoría's Online Reference