Apple Final Cut Pro 6 - Manual (Page 883)

98 Part I Audio Mixing
 If there were keyframes in the clip prior to recording keyframes: The audio level or pan
values are interpolated from the level of the last recorded keyframe to the level of
the next keyframe.
Modifying Recorded Keyframes
After you’ve recorded keyframes for a series of clips on a particular track, there are two
ways you can make modifications to the levels you’ve set with the Audio Mixer: by
using the Audio Mixer or by modifying keyframes in the Viewer or Timeline.
Using the Audio Mixer to Record over Previously Existing Automation
You can use the Audio Mixer to make further changes to audio clips in your sequence
that already have audio level and pan keyframes applied. How these changes are made
depends on whether or not the Record Audio Keyframes button is selected.
 If the Record Audio Keyframes button is selected: Changes you make with the Audio
Mixer during playback create a new set of keyframes, completely overwriting any
previously existing keyframes. Changes you make while playback is paused insert
new keyframes at the position of the playhead.
 If the Record Audio Keyframes button is not selected: Changes you make with the
Audio Mixer during playback do not create new keyframes. Instead, existing
keyframes are modified to match the levels set when the playhead passes over them.
Individual keyframes can be adjusted if the playhead is directly over them. If the
playhead is between two keyframes, the level of both keyframes is changed to adjust
that entire section of the overlay.
Playback stopped here.