While iMovie for iOS is a technological tour-de-force that somehow crams a complete video editor into the limited real estate of an iOS app, it does have its Achilles Heel -- a less-than-stellar ability to work with audio. Macworld author, TidBits Editor, and all-around nice guy Jeff Carlson, who also just happens to have written The iMovie '11 Project Book for Peachpit Press, has written a nice roundup of audio workarounds to help you with iMovie for iOS.
While I won't spoil the three well-written tips by repeating them here, I will give you an idea of Jeff's hints for getting the most out of audio in iMovie. The first addresses the fact that navigating the song list in iMovie's Audio pane is incredibly tedious. To fix this, Carlson suggests creating Smart Playlists in iTunes that ignore those songs with DRM that can't be used in iMovie videos.
Carlson also notes that iMovie for iOS has a limited number of sound effects. This can be remedied by finding audio files on your Mac that you wish to use in your movie (from iMovie sound effects or GarageBand), opening them in QuickTime Player, exporting them to your hard drive, and then adding the file to your iTunes library before syncing to your iPhone, iPod touch or iPad.
Jeff's final tip deals with the iMovie for iOS problem of not being able to use a song track shorter than 60 seconds in length as a background song. If you've needed a workaround for this, check out the post on Macworld or consider buying his book.