Very good music !
I'm not sure if you are aware, or if it's intended, but the ShareAlike version of the Creative Commons would force developers to release their game under the same license, if they want to use it.
I think (I am not a lawyer, but this is the type of response that you can find on the web).
Edit:
"Please contact me if you want to use tracks from this soundtrack in your video game, or if you want to commission some new music : oragus2@yahoo.com." I guess it's intended, I was wondering since you have another asset under the "normal" CC-by, my bad.
If someone would want to to make an open source game, and use your assets, it would still be difficult though.
I guess the CC-BY-SA is nice (made for) when it is expected that the derived product is of similar nature as the initial product.