Whilst it is true that the tune of Gymnopédie No. 1 is played at the beginning of the film, it is not the piano version but rather the orchestral version orchestrated by Debussy. For some unknown reason, Debussy changed the numbers of the Gymnopédies: thus the orchestral version of Gymnopédie No. 3 bears the tune of Gymnopédie No. 1!
In the credits, Erik Satie's Gymnopédie No. 3 is listed. However, it is Gymnopédie No. 1 which is played in the film.