If you overlap clips on the same track, a linear crossfade is created automatically by default. 
	 
You can change this behavior with one of the preset crossfade modes or by creating a custom curve to control the crossfade in the Crossfade section of the 
		
Time Editor Clip contextual menu. 
	 
To create a custom crossfade between clips:
- Right-click on the crossfade to open the 
		  Time Editor Clip contextual menu. 
		
 
- Select 
		   and choose 
		  Custom Linear or 
		  Custom Spline to base your custom curve on an existing curve type, or select 
		  Edit Custom... to explore creating your own interpretations of the crossfade based on the presets. 
		  
If you choose 
			 Edit Curve, the 
			 Graph Editor opens with a crossfade curve that you can edit. 
		  
 
		  See the 
			 Time Editor Clip contextual menu Crossfade section for descriptions of crossfade types.