Trimming looped clips can be done using the Trim tool, the Loop Trim tool, or one of the Trim Clip commands. The Loop Trim tool trims the entire looped clip. The Trim tool trims only the individual loop iteration while increasing or decreasing the number of loop iterations to fill the total length of the looped clip.
If the source clip is extended to the left by using the Trim tool to change the total length of the looped clip, the source clip is moved earlier in the Timeline and loop iterations fill in up to the point where the last original loop iteration ended. If the trim to the left is part of the source clip’s length, the source clip is not moved and a partial loop iteration is created to the left of the source clip. This is a powerful feature that lets you make quick changes to your arrangement by using partial loops as upbeats, or by extending looped sound effects or ambience earlier in a film score.