Composed in August 1931 in Wilm (Alsace region), this piece is for solo harpsichord or solo piano. It is dedicated to the harpsichordist Pauline Aubert and was published as a set with "Prélude à deux" (for two harpsichords or harp and piano). "Prélude à un" and "Prélude à deux" are essentially the same piece; "Prélude à un" is a concise solo arrangement of the essential parts of both lines from the duet-style "Prélude à deux". It begins in G Mixolydian mode in 6/8 time and concludes on a C major tonic chord. The ancient mode imparts a certain archaic flavor.

The piece freely develops around two main musical ideas: "Gracieux et souple" (graceful and flexible) at the beginning, and "Tendre et pathétique" (tender and pathetic) immediately following. The metronome marking, present only in "Prélude à deux" and absent in "Prélude à un", indicates the composer's intention to slightly reduce the tempo of the first idea before entering the second. These subtle tempo fluctuations can only be understood by referring to the score of "Prélude à deux". A comparative study of both versions will be essential for performance. The understated quality, like a fleeting gust of wind, resonates with the refined elegance of French harpsichord works from the Baroque period, which constituted a major part of the dedicatee's repertoire. Compared to "Prélude à deux", which features characteristic three-dimensional sound accompanied by polyrhythms, "Prélude à un" is less overtly modern. Instead, its unique, somewhat hesitant narrative style comes to the forefront, emphasizing its intimate character.