After all of the elements have been assembled onto separate reels and checkerboarded, the sound is ready for "re-recording", "mixdown", or
"dubbing"—as the process is known as. (Although some people also think of
foreign language replacement as "dubbing", that is not the correct usage of the
term. In Hollywood, "dubbing" means mixdown—not A.D.R. and not language
The first step are the "pre-dubs". This involves pre-mixing all of the
individual checkerboarded tracks of each element down to just a few in number.
Since, on a major motion picture feature, there can easily be as many as sixty or seventy individual tracks for every one reel of picture (approx. 10 minutes worth), and ten or eleven reels of picture to a full length movie—we are talking about a truckload of sound!
On a smaller show, such as a documentary, there may be only several individual tracks.
Using a geometric (or pyramid) type progression, all of these reels are eventually mixed down to a manageable few. For instance, let’s say there are 5 production dialogue reels, and 3 ADR reels. Eight reels, just for Dialogue, is difficult for one set of hands to manage. But all of these tracks could be mixed down to just one or two Dialogue reels. Then we pre-mix the fifteen or so reels that make up only the ambient backgrounds, and pare those down to just two or three. Similarly, reduce forty or so sound effects and Foley reels to just three. And so on.
Now, we are ready for the final mixdown. No longer are there sixty reels, but perhaps nine. These nine, which now include Dialogue, Effects, Music, and Narration can now be mixed down to their final composite levels in relationship to each other.
However, in real life, the elements are not actually combined into one monaural track. Instead, they are mixed down to three monaural tracks—Dialogue, Music, & Effects—all on the same piece of sprocketed film (known as fullcoat or three-stripe). Producers keep these three elements separate in case they should ever later want to modify the finished film, such as by replacing the English dialogue with a foreign language, or updating the music to appeal to a different audience.
It is because of this eventual mix to a "DM & E" that editors strive to
isolate as many effects as possible from the production dialogue tracks. That way, the dialogue can be replaced without having to replace all of the sync sound effects that would be lost with it.
On a stereo release, the mixers would end up with a DM & E for each stereo channel. Television would require two: Left, Right. 35mm stereo requires four: Left, Center, Right, Surround.
70mm, and the new digital release formats use six: Left, Center, Right, Sub-woofer, Left Surround, Right Surround. The Sony SDDS uses 8 channels, adding Left/center and Right/center to the six above.