I'm saying that the musics in vanilla (don't have any expansion) can be kind of heady in the wrong sense of the term. Particularly the mid/late eras ones. Strangely, I'm pretty never bored with the early era ones.
I think that making the link between the era and the music is not so smart. some kind of classical tracks can be very heady when in a loop, particularly when playing Civ5 and the stupid AI. The music bores me so much sometimes that I can't prevent myself to go into a speach delirium, like : "pd, va!", "espèce de petit pd de merde" (singing in a loop) "va te faire mettre fils de pute" etc. not remembering the exact words but I like to sing those big words in a loop. (french insults)
If the game were less boring (my games especially are boring, Prince too easy King too difficult) and the musics less heady, i may play the game more seriously.
That's why I think developers should create their own musics in a way they can be heared 1000 times without boredom.
I remember however Civ2 war music, it was barely not music just drums, it could last a very long time and was heady as hell. The positive point is that I sometimes play it in my head, particularly when i think about Civ series. That's a fact : I like this "music" despite its headyness, because at least it was frank : you were at war, and the drums was all over the place. It was very circonstancial and basic, I think all the sounds of Civ2 were basic, circonstantial, appealing and damn efficient. Of course, the "fire !!!" sound may sound a little kitch nowadays in term of gamedesign, but come on... it was so enjoyable ! WAR DRUMS, "FIRE !!!" "VROOOOO CRASH", etc. I think devs should try to reproduce this, because it was so good. Maybe it's just nostalgia after all, Civ2 was very iconic and sounds had to be too, maybe it would not be necessary in a nicer and smoother game, I don't know.
All in all, I'm seeing that headyness can be good. But I don't think every track is equal. Classic music becoming heady is not the goal. That's why it's so much a pain to listen. It feels gay and inapproppriated. heady music being heady may be good however. Let's not do things by a half !