The soundtrack closely accompanies the film's emotions and is primarily based on chants performed by the monks during the liturgy of the hours. The choice of chants and their integration into the script were overseen by Henry Quinson, with rehearsals directed by François Polgar.

The album includes fifteen excerpts: three spoken texts, eleven sung prayers, and a symphonic piece from Tchaikovsky's ballet Swan Lake, used during the monks' last supper. The texts are spoken by Michael Lonsdale and Lambert Wilson, while the Our Father is recited by the seven monks. The other chants, specific to the Cistercian Order of the Strict Observance, are performed a cappella by the actors, enhancing the dramatic intensity. According to director Xavier Beauvois, this collective vocal work contributed to the cohesion of the actors.

The trailer and the final scene also use the second movement of Beethoven's 7th Symphony, heard during the monks' departure to their execution.