It seems like all bards in the game are in the favor of the Imperials. They all sing the song "The Age of Aggression." I haven't met a bard that didn't sing this, does this mean they are all trained to spread the influence of the Imperial Legion, to side with them and show the problems caused by Ulfric? It makes sense though, the bards college is in Solitude which is the headquarters for the Imperial Legion in Skyrim. And has anyone seen a bard that was in the favor of the Stormcrackers, err Stormcloaks?

Bards in cities controlled by the empire sing age of aggression, bards in cities controlled by the stormcloaks sing age of oppression.

This. They're the same tune and very similar lyrics so it's possible you just didn't notice the difference.

I didn't notice this, maybe since I assumed too much, also I'm not on the western region, I am usually on the eastern side. Good to know though, the bards singing oppresion can now die. Thanks to you.