I think that background music on a site almost cheapens it. I mean even if the music is really good or really relevant to what I am viewing you are going against the whole revolution and point of the internet in general. I am mean the whole thing about the internet that makes it so popular and so regularly consumed is I get to choose what media I consume from it. So if I like videos, I watch videos, I don't want a video shoved in my face, same applies with music, if I wanted to be listening to something I would be already listening to it. Now it is a great add on to a site, but you have to give the surfer who is consuming your content the choice of whether or not they want to listen. We are in an age of media snackers, people will consume content they want when they want, they have the ability to do so and you need to respect that power they have been given. If your music is good enough in the background of your site, people will play it and listen to it, you have to give them the choice though or they won't give you the time of day.
Sorry for a long post from a junior memeber or Newbie .. but that is just my two cents
