A re-recording mixer in North America, also known as a dubbing mixer in Europe, 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, television program, or television advertisement.
The final mix must achieve a desired sonic balance between its various elements, and must match the director's or sound designer's original vision for the project.
Those tracks in turn originate with sounds created by professional musicians, singers, actors, or Foley artists.
In the dialog premix the re-recording mixer does preliminary processing, including making initial loudness adjustments, cross-fading, and reducing environmental noise or spill that the on-set microphone picked up.
They also modify individual sounds when desired by adjusting their loudness and spectral content and by adding artificial reverberation.