Vixeod, I hope this helps. I realize it's been some time since this was written but, I just came on board. Any way, I hope this helps, who knows you might have figured this out by now, if not, here goes.
Go into SHOW MEDIA SELECTOR. Then go into MY VIDEO find the video footage you're working on and RIGHT CLICK. It should say EXTRACT AUDIO... Don't Forget to go to FILE NAME: and name it. Now you should be able to move it to the Music Track or what ever track you want. Hope this helps.