I personally loathe background music on a website. My client has opposite feelings on the subject. I added music because the customer is always right, though I'd like to revisit the subject with them.
Almost everyone would agree that it is annoying and wastes precious bandwidth but are there any usability studies or a recommendation for someone esteemed in the profession that can provide a valid argument against background music?
Metrics. You'll never be able to convince a business person with an emotional answer.
If you investigate the situation empirically you'll be able to give them something irrefutable.
I would would try an experiment: (get google analytics)
Have the server randomly serve up the different pages for a couple weeks (until you get a significant data) and see what happens.
Maybe we're wrong (I hate music too). I hope your customer is wrong, but who knows.
You could also add a survey link and try to get people to answer that as well (but without an incentive that might not work)
Stats can be your friend here :)