The e-mail you received is a little weird, but I think I can clear up the license situation somewhat:

Originally Posted by Letha Allen
You are free:
to Share — to copy, distribute and transmit the work to Remix — to adapt


That's an excerpt from a Creative Commons license, like the one I use for my music:

http://creativecommons.org/licenses/by-nc-sa/3.0/nl/deed.en

(Note that the owner of the song may have employed a different version of the license; there are a few options to choose from)

Basically, when you release a work under a Creative Commons license, you are telling people what they can and cannot do with your work. In my case, I'm okay with people sharing my songs and making different versions (derivatives), provided that they do it in a non-commercial fashion and share the (new) works using the same license. (For commercial uses, I have a different license)

If the owner of this song has indeed licensed the work under a Creative Commons license that allows sharing and remixing (which your excerpt suggests), then you don't need his (or her) permission to add lyrics and vocals. That permission has already been given to you by means of the CC license!

Two gotchas:
- If the license is "NC" or "Noncommercial" (the crossed out dollar symbol), then you cannot use the song or its derivative commercially (unless you get permission from the author directly, which he may or may not grant you)
- If the license is "SA" or "Share Alike" (the circular arrow symbol), then you have to license your version using the same CC license.

Does that make sense? If you need further clarification on the Creative Commons, let me know!

Jim Offerman ~ inspirational pop music
blog - follow me twitter - buy 'Start Here' on bandcamp!