Apple Final Cut Pro 7 - Manual (Page 681)

To create a stereo pair
1 Select a pair of mono audio clip items in the Timeline. (Use the Command key to select
the second item, if necessary.) If you click one item of a linked pair, the other item is also
selected.
2 Choose Modify > Stereo Pair (or press Option-L).
The stereo pair indicators appear on the selected clip items in the Timeline.
Stereo pair. Green arrows
indicate a stereo pair;
underlines indicate
linking. Mono clip items (linked).
Underlines indicate
linking. Mono clip items
(unlinked)
681 Chapter 43 Audio Editing Basics