The Mysterious Melody AKA Ce soir les souris dansent(1956)

The Mysterious Melody is a French crime film centered on a puzzling murder investigation. When an elderly violin maker is found dead, detectives have little to go on except a haunting melody heard by a blind street musician on the night of the crime. Unable to identify the song, the inspectors submit it to a popular radio contest called "The Mysterious Melody" in hopes of uncovering leads. As they methodically interview suspects and piece together clues, the two investigators gradually close in on the killer. The film unfolds as a classic whodunit, relying on the mysterious tune as the crucial thread connecting the crime to its solution.