I find the concept of "signatures" super interesting with music, and fun! I'm not too familiar with the Age of Empires series of games but I got some friends who gush about them and I've always got a soft spot for any older PC games. But these are some tasty tracks and thanks for pointing out The Bovinian Derivative, it's got a cool atmosphere about it.
I think it's also fun when the usual sound team behind a series are absent for an entry for whatever reason. Donkey Kong Country 3 is the first example that comes to mind for me, but I think it's cool hearing a different perspective on things.