デフォルトのトランジション

Final Cut Pro

In order to add a default transition with media handles, select a clip or edge of a clip (an edit point) and press “Transition”.

When you add a transition to a video clip with attached audio, Final Cut Pro X automatically applies a crossfade transition to the audio. If the audio is detached or expanded from the video, the crossfade is not applied. But you can add it separately to an audio clip.