While Estampes was the first work to establish Debussy's so-called "Impressionistic" style in piano music, it can be said that this collection of two books of Préludes further developed it to a state of completion. Consequently, all the pieces in this collection are masterpieces that showcase Debussy's unique individuality.

The 12 pieces of Book I were composed between 1909 and 1910. The titles of each piece were written in small print in the margin at the end of each piece, a consideration by Debussy to prevent listeners from being constrained by preconceived notions.

1. Danseuses de Delphes / "Danseuses de Delphes"

This piece softly depicts a dance dedicated to the gods at the ruins of the famous Temple of Apollo in Delphi, an ancient Greek city. It is said to have been composed with inspiration from sculptures in the Louvre Museum.

2. Voiles / "Voiles"

This piece, which Debussy himself described as having a "supple and caressing rhythm," skillfully employs the whole-tone scale to exquisitely express gently undulating waves and wind.

3. Le vent dans la plaine / "Le vent dans la plaine"

The wind blows quietly, sometimes a little strongly, across the plain. Such moments of nature are meticulously depicted.

4. Les sons et les parfums tournent dans l'air du soir / "Les sons et les parfums tournent dans l'air du soir"

The title is taken from a line in Baudelaire's poem "Harmonie du soir" (Evening Harmony). A languid and melancholic mood flows through an indeterminate rhythm.

7. Ce qu'a vu le vent d'ouest / "Ce qu'a vu le vent d'ouest"

The west wind in France is usually strong, and its fierce raging is expressed with technical boldness.

8. La fille aux cheveux de lin / "La fille aux cheveux de lin"

This piece was composed under the influence of the poem of the same name from Leconte de Lisle's poetry collection Chansons écossaises (Scottish Songs). In this poem, "The Girl with the Flaxen Hair" is described as "a beautiful girl with cherry-red lips, singing of love with the larks, bathed in the bright summer sun."

10. La cathedrale engloutie / "La cathedrale engloutie"

It is said to be based on a Celtic legend passed down in Brittany. This legend tells of a cathedral swallowed by the sea that rises above the waves, beginning with the quiet sound of bells echoing in the sea, and culminating in a powerful surge as the cathedral majestically emerges.