An audio engineer who performs the sound mix, which is the process of re-recording multiple reels of track to produce one final soundtrack, which includes all dialogue, "looped" dialogue (ADR), music, sound effects and foley, and narration (if any), for each reel of picture. During this process, the sound mixer can adjust the volume and equalization of the sound units on the individual reels in relation to each other, as well as produce effects such as fade-ins, fade-outs, and crossfades.