Just been listening through my MxO soundtrack folder and realised something. Something horrible. Something wrong. Something evvvviiillll.
The awesome-ness of the secondry mission music tracks (as in the more dramatic, tense, heart pumping and overall much better than the primary ones) can't be heard, to my knowledge, anywhere in game.
I was just wondering, is this indeed the case? Anyone heard em used ingame?
If not, dear lord they should be.
Although i'd say only for something special, the dramatic style would have to be accomanied by something equally awesome. Like some sort of important questline with a big ol boss or something.
And for anyone who doesnt know what the hell im on about...
Zion Secondry
Merv Secondry
Mach Secondry
Neutral Secondry
Niobe Primary
Niobe Secondry
EDIT: Oh brainstorm. These could be used for critical missions while the primaries can be used for standard and archived missions. The neutral secondry track could be used for pandoras box while the primary is still used for neighbourhood contacts. And niobe... err... that can go somewhere else 
EDIT2: Oh and before anyone comes up with rarebit's lil tidbit of times past about music being hard coded in with controllers keep in mind rare must've added new controllers for the mission archive ([archived] and neutral music tracks) so in theory he could just make another set of new ones for seperating criticals from standards.
