The same thing just happened to me - I uploaded an unlisted video that we created in iMovie using it's ambient sound effects which are royalty free for users. Within minutes I got 2 copyright claims - one from IODA for a piece of music that bears no resemblance to the iMovie effects. The second from RumbleFish claiming that our video contains music from Royce Campbell's "Breath of Life". I checked out this song on Amazon and found that the short preview clip was the same sound as one of the iMovie ambient sound effects that we used in our video. Very interesting! Either Royce Campbell licensed his music to iMovie for free use by users or he ripped off the iMovie effect and is passing it off and allowing RumbleFish to make fraudulent copyright claims on his behalf for a sound effect that is not actually his, but from iMovie. Or perhaps RumbleFish do not realize this? I plan on notifying Apple of this false claim by RumbleFish and the iMovie copyright breach by Royce Campbell.
BTW - here's the piece of music from Amazon that is the same as a sound in iMovie -- for those familiar with iMovie you will recognize it. (I took your advice and put a comment on this as well as the IODA piece which bears no resemblance.)
I've also disputed the copyright claims to our video by both IODA and RumbleFish -- which brings up a second point - how can 2 artists be claiming the SAME piece of "music". Obviously there's a scam going on by both IODA and RumbleFish that YouTube is allowing to happen.
I have contacted RumbleFish directly but have no email for IODA to register a complaint at.
Basically both companies are doing this to fraudulently monetize other people's videos. I wish them luck with this one since it's an unlisted video only meant for a few people.