My audio transitions aren’t likely as clean as yours. What I tend to do is split the track in iMovie as close as I can around the line that I want to get rid of. I then separate out the audio, shorten the video on one side or the other until it reaches a new camera shot, then overlap the residual audio, fading the pre-cut audio out, while fading the post-cut audio in.

Often this results in a transition that blends pretty naturally to my ear, but I don’t use any fancy speakers, and I’m not an audiophile. There are definitely times when I can’t make a cut like this due to a more dramatic change in the background music, though sometimes I can hide that by fading in and out a third layer of audio with other background noise or music.

I ended up cutting Rex’s introduction. Cody gets introduced while Rex just takes his helmet off offscreen.