For some of the Audio files there named. All the anthems when opened with BigGUI are in alphabetical order and named.
In fact looking at the file now for chants.big, there seems to be two for Australia at the top, an S*** load of ones named EngGen001 and stuff. Then there is general ones and one each for nz, ireland and south Africa. They are all .asf which is the same as the menu music. I'm gonna go out on a limb and say that it is possible