Changing Music at a Certain Point

I am in search of a script (if it even exists) that will help me put in some cool music effects in my game.

So, as a brief description: If you've played Banjo-Kazooie or Banjo-Tooie, you may remember that the music changes slightly when you enter a body of water. The instruments become more subdued and a little less lively. BUT the point is that the music does not stop when you enter the body of water, it just keeps going on where it left off, just with a different instrumentation.

I have the means of composing both versions (a normal version and a modified version), but now I just need a script that will allow me to:

• End "Version A" immediately or have it fade-out.
• Begin "Version B" immediately or have it fade-in.
• Have Version B start at the same point (Say... 1 minute and 13 seconds) where Version A ended.

If anyone knows of a script that is capable of doing this, or knows of someone who can make a script like this, then I'd be grateful. :)

I know there was a script like this in the last ReStaff release, (don't have the link on me) but I don't know if it would work for this kind of thing, as the demo only showed its use in battle.