Originally Posted by caddywumpus
You can do it in either or both. Just copy the audio in iMovie and paste it into the R channel. If you want it to sound stereo, offset it by a few milliseconds.
You could also export the audio file from iMovie into garageband and do the same thing there, then move it back to iMovie.
I thought that I could do that also at first. It's not that simple! Garage Band treats an audio track as one entity, Right and Left channels can't be separated. If I copy the track, I wind up with a duplicate of the left channel. I can't make it move to the right.