I recall a filter for winamp from a few years ago (I don't use winamp anymore) that filtered out voices from a track. The only problem was that if there were other channels than the main voice channel on the track that had backup vocals, you get a kind of ghostly sounding background vocal here and there.
maybe winamp has a better version now or another program might have one. otherwise, there are karaoke versions of songs available in some music stores as I recall, but I've never been interested in them so I don't know how widely available they are. I should ask my brother since he's into shrieking bad songs while he's drunk at karaoke bars...
Anyone know of an easy way to remove 'voices' from soundtracks? In other words, take a normal song and end up with a kind of 'karaoke' version?