In Blue Velvet, Lynch uses sound and music in several different ways, to enhance atmosphere, establish mood, but also sometimes to help telling the story itself.
Indeed, first, Badalamentis score contributes to complete the films themes. Lynch depicts a seemingly beautiful and quiet small town, but like everything, a hidden side reveals evil, pain, madness. The music denotes this hidden side, and even mystery and darkness. But particularly, it contrasts with the 50s (stereotyped as the happiest Americans years) style pop songs heard throughout the film, that indicates the appearances of joy and peacefulness.
Plus, the score often immerses the audience in a film noir mood, a detective film or something alike. It creates a certain type of genre mixture, as this music contrasts with an often colorful image and more ordinary characters than in noir films. Thus, music brings a new dimension to the film and doesnt just describe the images ambiance.
Furthermore, music can be a narrative by itself in some scenes, for instance in the sequence where Jeff and Sandy just met and theyre walking at night. On screen, we see two people talking and even having fun she laughs to his chicken walk. Contrastingly, the music is tormenting and stressful. It puts the audience in a more tensed mood, like if this encounter showed the beginning of trouble (she shows him Dorothys building).
In the opening sequence that symbolizes the whole film, a contrast is already introduced between the generic orchestral music; and Bobby Vintons romantic Blue Velvet played non diegetically, over the images of a happy American town. Its kind of a nostalgic sequence from the happy times of the 50s. All the supposed diegetic sounds are first off (fire truck, children actually quiet, TV ), and the first that we hear is the watering and then the garden hose making strange noises. But the music continues playing, along with the amplified and disquieting noises and sound effects of the pipe; even when the man falls down, as nothing happened. It starts fading when the camera pans to the grass and we enter it slowly. The sound effects are heightened; the sound becomes more and more disturbing and weird, creating the feeling that were entering a dangerous place. We see the beetles struggling and their sound is clearly amplified, which contributes to stress the darkness of what might be hiding underneath the surface.
Then, we come back to the vision of a happy town, Lumberton, with a joyful radio jingle that replaces the sound of the beetles. The radio voice makes us feel that its a small, cozy town where everyone knows each other; and the announcer seems friendly and enthusiastic, which takes us back to the illusion of...