A re-recording mixer, (or just a mixer) is a post-production audio engineer who mixes recorded dialogue, sound effects and music to create the final version of a soundtrack for a feature film or TV program. The mix must match the director’s or sound designer’s original vision for the project, and is considered the stage where the final sound of the film is sculpted out.
For material intended for broadcast, the final mix must also comply with all applicable laws governing sound mixing (e.g., the EBU R128 loudness protocol in Europe or the CALM Act in the United States).
During the “final mix” the re-recording mixer, guided by the director or producer, must make creative decisions from moment to moment in each scene about how loud each sound element (Dialog, Sound Effects, Foley and Music) should be relative to each other. They also modify individual sounds when desired by adjusting their spectral content and by adding artificial reverberation.