Doesn't the bard mention in his conversation that he is working on the 'ominous' piece? It seems reasonable that would be the default music.
Some people have run into a problem (in D2:ED and DKS) where if they leave the throne room before a musical selection has completed playing it will not be available again (some people had that happen just with specific pieces, some with any).
Xbox 360 long loading times (Heather Li reports a similar music problem a few posts down)
