Apple Final Cut Pro X (10.0.9) - Manual (Page 175)

Chapter 9 Edit audio 175
Create a crossfade manually using fade handles
1 Select two adjacent clips in the Timeline, and choose Clip > Expand Audio/Video (or press
Control-S).
The clips appear expanded.
2 Drag the end point of the first clip to the right and the start point of the second clip to the left
so that the audio portions of the clips overlap.
Note: Make sure to adjust the audio overlap to the length you want.
3 Drag the fade handles of each clip to the points where you want the fade to begin and end.
Crossfade Fade handle
To change the fade shape for each clip, follow the instructions immediately below.