Nothing more needs to be said.
Stormwind city theme (I love chanting and epic music, also extremely calming)
Ironforge city theme (See above)
Ashenvale (especially when "The Song of Elune" kicks in)
Arathi Basin (the tune made it so intense, especially when you were on your own defending a flag when all of a sudden some of your foes close in on you)
Some of the taverns (Lion's Pride was the name of one)
I thought I had forgotten most of the zone's ambient music but after listening to them on YouTube, I remember they're all great.
either thunder bluff of the undercity, nothing quite as calming as the instruments used in thunder bluff, and undercity is so.....bone chilling. you actually feel like some creepy undead eyes are watching you.
To me, I think the music of WoW is the best thing about the game. The game has had dips and peaks in quality for a decade now but the one thing that has stayed consistently strong is the music. Most games don't have such universally enjoyable and memorable tracks.
It really shows how game designers might change and the game itself with them but the music done by the same composers can always stay as brilliantly unique as it ever was, it really shows how important music is in games.
I just love the music outside of Ulduar. Don't have a link too it, but that's probably my favourite.