how to add music from an iTunes music video to iMovie

I am not certain whether copyright issues would prevent detaching the audio from a commercial or copyright protected video.

If you did detach it, it might not play in iMovie. However, it might be O.K. if the song is still for your personal, non-commercial use.

I am assuming that you have the iTunes video on your Mac as a .mp4 or .mov file.

Further assuming no copyright issues, you could put the video into an iMovie project and then do a Modify/Detach Audio. That would separate out the audio as a separate clip. Then you could delete the video.

Another way, which might pass muster, is to overlay the iTunes video onto a video clip in the time line where you want to insert the audio. Use the Picture in Picture feature to make the overlaying video very, very tiny, and then position it down in the lower right hand corner of the overlaid video beneath it. It would be invisible but the song still would play. You might even be able to move the tiny video off the screen altogether.

As I mentioned above, however, copyrighted materials may not play in iMovie, particularly audio. So you need to see for yourself.

-- Rich