Exporting audio in iMovie '09?

I searched the forum, but didn't really see anything that answered my question. I filmed some shows from a band that I played with a few months ago, and the audio was surprisingly decent at a few of the shows, so I'm trying to figure out if there's a way to export the audio and then bring it in to Garageband so I can separate the songs to use in iTunes. Any help would be appreciated!