Apple Final Cut Express 4 - Manual (Page 305)

Chapter 22 The Fundamentals of Adding Clips to a Sequence 305
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Since the audio and video items of each edited clip are linked, selecting the video clip
item also selects the audio clip items, and edits you make to one are automatically
made to the others. For example, if you move a video clip item from track V1 to track
V2, the audio clip items move from tracks A1 and A2 to tracks A3 and A4.
Video and audio clip items can be linked or unlinked at any time. For more information,
see Chapter 30, “
Linking and Editing Video and Audio in Sync ,” on page 429.
Video clip item on V1
Audio clip items on
A1 and A2
...the audio clip items
move as well because
they are linked.
When you move a video
clip item to a new track...
The video clip item is
now on V2.
Linked audio clip items
are on A3 and A4.