Apple Final Cut Express 4 - Manual (Page 499)

Chapter 33 Performing Slip, Slide, Ripple, and Roll Edits 499
VII
To create a split edit using asymmetrical editing:
1 Select the Ripple tool.
2 Hold down the Option key, then click the Out point of a video clip to select it.
Holding down the Option key while selecting an edit point selects only that point,
ignoring any other items linked to that clip.
3 Hold down the Command key, then click the In point of an adjacent audio clip.
Holding down the Command key while selecting an edit point allows you to add edit
points to the current selection without deselecting previously selected edit points.
Current Out point of
outgoing video clip
In point of incoming
audio clips
Intended video
edit point
Before