I'm a big "Myth" fan and after hearing the roaring of cellos every time I start Myth 2: Soulblighter I decided to look up the music online. Since the game is comparatively old by today's standards it was a lucky hit I found the songs on youtube. Here is my favourite from Myth: The fallen lords
http://www.youtube.com/watch?v=8hTgvNsqb9Y
And again on piano, although I find this version much better
http://www.youtube.com/watch?v=X0JHB2u_rEM
The links I posted are to a song called "The Siege of Madrigal." After much wikipedia browsing I realized that the company responsible for the divine substance known as Myth is Bungie. Yes, that bungie. Before it was Master Chief's Bungie the company put out the Myth series and the undeclared predecessor to Halo, Marathon. In a kind of homage move Bungie made the song unlockable in Halo leading many Halo fanboys to proclaim "LOL wtf's 'Myth?' this song is from Haaaaaaalo nubs!"
Another great soundtrack is the diversity of music coming out of Sid Meier's Civilization series. Many of the games, when viewed from the apropriate hight, have a very nice world music soundtrack. If you can't find a torrent for some of this stuff you can always steal it from the games' music folder.