I wasn't really going for Magic with the music-based thing >.<;; but that's one way of looking at it. It's supposed to be more psychic/psyche based than magical. But I suppose it's all different names for the same thing. 

Ramzam has pretty much summed it up well. Two identical worlds that were once one, split apart. Developed similarly, though separately. Collided together by a scheming group who know the history, but not the full results of what happens, but have their own agenda for putting them together. A group of people, some of them fuzzy, in mecha-type vehicles, fight to stop the organization, and control the damage. 
Finding out what Elysium's plan really is and what it will do will be a part of the plot. 

It sounds a lot simpler that way than the ramble-post I put up originally, and less disjointed.