Apple Final Cut Pro 7 - Manual (Page 127)

Chapter 6 Working with Audio 127
Click the Level Keyframe button to add an audio level keyframe to the clip at the 5
position of the playhead.
Drag the Level slider in the Viewer’s Audio tab to 0 (zero) to increase the audio over time.
6
Drag the slider until the
Level field displays 0 (zero).
Press the Home key and play the clip from the beginning to hear how the audio level 7
increases.
Position the pointer over the pink audio level overlay line in the Audio tab and drag up
8
or down to change the audio level.