When the title character of Xavier Giannoli’s movie, an amateur soprano, lets rip with a big aria from “The Magic Flute,” the notes are not even in the same ZIP code as Mozart’s. Yet Marguerite, played with naive sweetness by Catherine Frot, has no idea that her voice sounds like a cat requesting dinner. And because Marguerite is rich, no one — not a critic (Sylvain Dieuaide), not her butler (Denis Mpunga) and certainly not her cheating husband (André Marcon) — dares to tell her.

It’s an often witty, smoothly shot film with a couple of extraneous subplots and some last-act psychology that feels contrived. But Frot shines. While the premise (inspired by the true story of tune-challenged American socialite Florence Foster Jenkins) could be as cruel as “Carrie,” Frot’s would-be diva is achingly sympathetic.