Marion-Rivard, along with most of the choir members we see in the film, is a non-professional actor; Archambault cast her while developing the story after a period observing Les Muses. Much of the pain and joy of the members' lives are projected naturally in the rehearsal room, and Archambault films in such a way that the professional actors merge with them seamlessly: Landry's Martin is a believable boyfriend, tender and devoted; Mélissa Désormeaux-Poulin (who starred in fellow Quebecois director Denis Villeneuve's moving Incendies) is both stern and empathetic as Gabrielle's responsible older sister.
Most importantly, Archambault has a rare light in Marion-Rivard, whose wide smile is infectious: When she sulks, it feels like the whole world is tumbling down. The film that follows her is unpretentious to a fault, and consequently stumbles occasionally; the sex scenes drag a little, and a few treacly soundtrack selections grate in contrast with the heartfelt music delivered by Les Muses. But Archambault is fluent in small, self-contained moments. Even as their guardians are forced into difficult conversations, Gabrielle and Martin's private exchanges ring true.