Wikia

Jason Hayes is a composer who wrote some of the themes and music for World of Warcraft and World of Warcraft: The Burning Crusade.

WoW Themes

Alliance Azeroth tavern music (now replaced by a newer version by David Arkenstone)
Angelic music moment (commonly heard in night elf settlements)
Enchanted forest themes (mostly heard in Teldrassil and Ashenvale)
Evil forest themes (such as those played in Duskwood and Tirisfal Glades)
Forest themes (such as those played in Elwynn Forest, as well as those played in Darkshore and Moonglade)
Haunted musical moments
Jungle themes (such as those played in Stranglethorn Vale)
Magic musical moments
Mountain themes (such as those played in Dun Morogh)
Plains themes (such as those played in Thousand Needles)
At least one of the sacred moment themes
The spooky musical moment
The swamp musical moment (commonly heard in satyr camps)
Horde tavern themes (the two 'tribal drum' themes, heard in troll villages - the undead tavern music is credited to Derek Duke)
Volcanic themes (such as those played in the Burning Steppes and the Searing Gorge)

Caverns of Time (Hillsbrad exterior)
Caverns of Time (Hyjal exterior walk themes, one of which was co-authored with Derek Duke)
Ghostlands 'Shalandis' walk music (just one of the three themes, a remake of the "angelic" moment, co-credited with Russell Brower)