Apple Final Cut Pro 7 - Manual (Page 502)

For example, if you want to edit the video clip item in the Viewer into your sequence,
but you don’t want the audio clip item, you can simply disconnect all of the audio Source
controls in the Timeline, leaving only the video Source and Destination controls connected.
Performing an overwrite edit adds the video portion of the selected clip to your sequence,
ignoring the source clip audio.
The audio Source controls
are disconnected from the
audio Destination controls.
The v1 Source control
is connected to the V1
Destination control.
Disconnected Source controls remain disconnected even when you open a new clip in
the Viewer. This is true even if the clip has a different number of video and audio clip
items than the previously opened clip.
502 Chapter 34 Working with Tracks in the Timeline