Apple Final Cut Express 4 - Manual (Page 631)

Chapter 42 Mixing Audio in the Timeline and Viewer 631
VIII
To set and adjust subframe audio level keyframes:
1 Open the clip in the Viewer and click the Audio tab.
2 Move the playhead to the edit point that’s causing the click by pressing Shift-I or
Shift-O, or by using the Up and Down Arrow keys to move from one sequence edit
point to the next.
3 Zoom in to the clip as far as possible.
4 Hold down the Shift key as you drag the playhead to the exact place where the click occurs.
When you’ve zoomed in
all the way, the playhead
in the Viewer is the width
of one video frame.