Ooh yeah! I just dealt some lethal intolerance on my Oblivion music folder by reviewing all music one by one and removing music that didn't quite fit Oblivion. It wasn't by listening to the whole song, but by skipping through in WMP and getting the gist of it. It's true that diversity is nice, but too much spice is too much spice. Nearly 3/4ths a GB of unnecessary music deleted. Why? To enhance Oblivion's intended epic atmosphere with music that follows instead of leading off track.

Things that stood out and had to go:

*Explore music of a Celtic woman trying to be African in a song provoking a sense of running naked through an uplifting African rainforest fantasy
*Explore music ripped straight out of movies and are wrong for the game because they are busy illustrating the scenes of the movie rather than being ambient
*Explore music destroying itself by breaking into too intense a music climix or by suddenly using modern instruments, or by being too cartoony
*Explore music trance
*Dungeon music using cheap synthesizer to sound like the Terminator's alternate vision mode
*Dungeon music trying to be too Exorcist and by having the male choir sing in Latin, it's not right for Oblivion
*Dungeon music trying too hard to be scary and throwing too much instrument sound effect at the audience
*Dungeon music ripped off from Diablo
*Battle music stolen from movies and don't work because it shifts between the good guys and bad guys, or even fanfares while they would be posing
*Battle music that is too ancient roman, too middle eastern, too viking, or some other that doesn't match Oblivion
*Town music being so over-sentimental that you can't look past it, or being too effective at being sad that it almost moves you to tears
*Town music being too dead serious or being the wrong mood and trying to make it work
*Any music that wouldn't fit the tone the game wants to present, or is ripped out of too recognizable a movie scene
*All trance music

So, are you an Oblivion music folder Hitler? Have you downloaded music packs and run an audition screening each file one by one? Did you previously throw all music into your folders like I did because I thought that more is better? How intense is your Oblivion music discrimination or else how tolerant are you for Oblivion music diversity?

My Oblivion music folder hasn't been touched once. I adore the Oblivion soundtrack, and wouldn't want to remove any of it!

That said, I'm probably going to be putting the Morrowind main theme into Oblivion. Not only is it a beautiful piece of music, but I think it would fit well in Cyrodiil.

True, but you're not removing anything. Only adding to it. My opinion of downloaded music is that there is a lot of bad, but some of it will appeal to you and still match Oblivion's lore more or less.

I've put a lot of music into my Morrowind and Oblivion folders over the years. I use only instrumental music and only music that, I feel, blends well with Jeremy Soule's music.

im thinking about putting all the sounds of TES games since morrowind in Oblivion

I haven't done so before and I'll probably leave the music as it is but now that you planted the seed I'm thinking there's got to be a fitting place for a few of my favorites pieces e.g. Flight of the Valkyries, O Fortuna from Carmina Burana and Soldier's Chant from Rome Total War.