I inherited some VHS footage (via DVD) of my sister-in-law's band playing a few gigs and I've decided to clean it up as best I can. Both the video and audio are pretty bad, but I've been able to make some pretty good improvements in the video using AVISynth. I know you can only polish a turd so much, but I'm hoping there's something I can do to make similar improvements to the audio.

The main problem with the audio is that there's a lot of background crowd noise (obviously) and the vocals and instruments tend to sound very muffled. I'll be using Audacity, unless someone can recommend another good free audio editor. I'd be very grateful for any tips, links to tutorials, etc. that might point me in the right direction.