Where can I find a free music software editor, where I can do things like shorten songs, or strip song vocals?

Audacity (www.soundforge.net) will help you edit music. However, there is NO software that will strip vocals. If anyone tells you there is, they are lying. It USED to be that you could do this, when things were mixed in a more primitive fashion. But now, if you try to strip the vocals, you end up with a big hole in the music, and the rest distorted. I am in the music business and have taught vocal music since 1971 - believe me, if there was a REALLY GOOD way to do this, regardless of cost, I would have it - I could use it every day. That is why there are so many other work-arounds, and karaoke tracks for sale. Once something is MIXED for sale, you cannot separate it out anymore - you can't take the salt out of the soup.