In the ign quakecon article, they talk about a door that wants "the music of life". Along with sounding alot like a demon door from fable, it seems like a gold indicAtion that the Pc will have some compacitly for music making.

Yes, at first I misread that quote to be "What is the music of life?" which sounds like the DB question "What is the color of night?"

However the door is actually asking, "Do you know the music of life?" and one of the answers seemed to involved singing or banging drums. I think you might be onto something - this could be the lair of an evil subset of bards that terrorizes the countryside.

Bard-o-mancers

Seriously, though I do think it's possible that the people behind the door are Bards and not Dark Brotherhood (unless the Dark Brotherhood are Bards in Skyrim - many bards could be assassins or spies). I'm thinking about someone like Mance Ryder

I support you, BootySweat, in your thoughts that the door is possibly relatred to bards.