: The guy who is doing this is named Nick Singer, who is a professional
: composer who studied at Oxford and the National Film School.
: --Craig Hardgrove
Craig, this is incorrect. I'm aware of Nicholas' remixes, of which (AFAIK) there are only two so far. The remixed soundtrack I'm referring to really sounds nothing like his work, nor yours. Not to mention, it's a complete set of all 16 tracks. It sounds a lot like the A1 soundtrack, but with richer sound overall. It might be a different set of QT instruments performing the Marathon soundtrack, but I kind of doubt that, as there just seems to be more depth and minor touches for it to be a simple instrument change.
I added a link to a song from the set in my first post. I'm not sure if I should upload some more in case someone might be able to identify some of the other tracks more easily and tell me where they're from.