Apple Final Cut Pro 7 - Manual (Page 139)

Chapter 6 Working with Audio 139
Balance the overall audio level of a sequence in the Timeline:
Position the Timeline playhead over the audio clip items.
1
Drag the slider of the Audio Mixer’s Master fader up or down to adjust the overall audio 2
output level of the entire sequence. You can use the Master fader to adjust the general
audio level of all the tracks in your sequence at once.
Master fader