Apple Final Cut Pro 7 - Manual (Page 985)

You might put one actor’s voice in track A1, and another actor’s voice in track A2. Narration
recorded with the Voice Over tool might go in track A3. Background ambience clips such
as wind and rain might go in tracks A4 and A5. Sound effects could go in tracks A6, A7,
and A8. Finally, four tracks for overlapping stereo music clips would be dedicated to tracks
A9, A10, A11, and A12.
If you’re working on a project that may be distributed to an international audience, you
should also keep your final mix separated into D, M, and E (dialogue, music, and effects)
and stems. This allows foreign distributors to dub over the voices of your actors without
losing the music, ambience, and effects that you’ve edited into your program.
Description Categories of audio tracks
This includes most of the audio that was captured with your video.
Whether or not you place each character’s lines in a separate
dialogue track is between you and your audio editor. Dialogue
Narration should be put in a separate track from dialogue, as it
probably has different EQ settings. Voiceover
Stereo music from any source could use up to four tracks, if you’re
doing complicated music edits or cross fades. Music
Ambient tracks include background tones, atmospheric sound
effects, and possibly room tone. Ambience
Effects include material from effects libraries as well as effects clips
you record yourself. If you’ve edited in Foley effects, they should
occupy a separate set of audio tracks. Sound effects
985 Chapter 60 Exporting Audio for Mixing in Other Applications