After playing around with Halo: Spartan Assault [Steam]'s music files, I decided to take what Original Soundtrack counter-parts matched and created in-game edits of them, so they can be flexibly edited to seamlessly loop as short or long as you want, whilst keeping their beginnings & ends.

You can download the full pack in .WAV format (as that fully preserves the loop, but makes the files very big): http://www.mediafire.com/download/sygrb878012w4sl

Otherwise, you can listen to the approx 10min loops I've prepared on YouTube through this Playlist (which it & the videos contain the download link too): https://www.youtube.com/playlist?list=PLV-GRqsVd9khYLdh18RS7YiOctem0R7FX

You can open them up in your video player & leave on loop, or put them together in Audacity, Sony Vegas, whatever audio software you may use, and have fun! Use them for whatever you please, that of course rests within Microsoft Studio's Content Usage Rules of course.

Although they're named after the game files, those names contain both the Mission Numbers & Music Titles, so knowing which one's which shouldn't be difficult to work out.