I haven't played War of Magic, but the music is okay. Its not as good as Age of Wonders 2 in my opinion, but its a similar style, a little more low key overall. Primary instruments seem to be strings and wind and overall I find it enjoyable to listen to.
There are a bunch of songs in the music folder, including different mood versions of the same song. I am guessing they change what plays based on the state of the game, though I never really noticed while I was playing.