hmmmm, ummmmm it seems like the eoth would just use the same sort of style of brooding orchestra as the empire music, just not the same song. but thats my opinion
for the rebels. certainly happy isnt a good word to describe the mood. more like triumphant. u know like the song "the throne room" from the end of episode IV, that sort of stuff for rebels.
idk mabe go cliche for the empire with orchestra and umm mabe alienish for the chiss, (warp and distort there music lots of filters) and for the rebellion, mabe trumpets sort of happy