Apple Final Cut Pro 7 - Manual (Page 992)

In your sequence, you can assign as many tracks as you want to the same audio output
channel. For example, you can assign tracks 1-4 to audio output channel 1 (mono). The
resulting exported audio file for output channel 1 would contain a mix of audio from
tracks 1-4. You can use audio output channels to group and mix multiple audio tracks
together during export. For example, you could assign tracks 1-4 to output channel 1,
tracks 5-8 to output channel 2, and tracks 9-10 to stereo output channels 3 and 4. This is
useful for exporting stem mixes for use in a final audio mix elsewhere. For more
information about assigning multiple audio outputs, see
“Assigning Output Channels
and External Audio Monitors.”
Example: Exporting 12 Tracks to Three Stereo Audio Files
Here’s a typical example illustrating how you might export multichannel audio from an
edited sequence. Suppose you’ve set up a sequence to have three stereo audio outputs
and 12 audio tracks.
The Audio Outputs tab of the Sequence Settings window would look like this:
And the sequence would look something like this:
992 Chapter 60 Exporting Audio for Mixing in Other Applications