The Piano Tuner (movie, 2011)

Adrien is a young pianist prodigy. He collapsed psychologically having failed in a renowned competition and henceforth works as a piano tuner. As remedy to this life, he invents a blind person's mask to penetrate into the intimacy of his customers. This subtlety allows Adrien to get back the taste for music. But since he sees things he should not see, Adrien ends up witnessing a murder.