IMovie videos freezing, music continues to play?

I'm creating a montage of some videos on iMovie with a song as the backing track, however I've hit a brick wall of sorts because I can no longer add videos without the clip I add freezing.  The music continues to play, but the video I add just freezes.  It doesn't matter what video clip I add (I've tried a few in case it was the clip that was causing the problem) but it happens to all of them.  The rest of the video plays fine.  I've made plenty of videos like this before and I've never faced this problem so I have no idea what it could be!  Any help would be much appreciated, thanks.


That's normal and as designed. The song will play out. You can pause it by pressing one of the volume buttons or use an app like 'Stop the Music' to completely exit the player.
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