I have put together a video from the photos off my camera and it's nearly finished apart from the musical soundtrack.

I made up a musical soundtrack using Audacity, I looked at the length of my video and edited the time on the music to match the time on the video, but something went wrong as it appears the soundtrack is too long as it ends suddenly rather than fades out as I edited the soundtrack. So what I would like to do is remove the soundtrack, redo the length of the soundtrack and then put it back. Unfortunately there does not seem to be an "undo" so I don't know how to do that.

Your help is appreciated.