Lukemac, I'd go for an evaluation to be sure. The avoidance of new things, the inflexibility around the area of special interest, the intensity of that interest are all a little atypical, though not enough to make an armchair diagnosis easy. If his social relationships are truly reciprocal, with give-and-take and genuinely flexible conversation about a wide variety of topics, it's unlikely he has AS; but my instinct is to be sure, especially since AS is usually missed in bright kids and you suspected PDD-NOS earlier.
It will take a while to get an appointment (there are often waiting lists with qualified people)-- during that time you can make notes so that you have lots of info to give the evaluator. They will need to know things like how much time DS spends with the music per day if left unchecked; what is the nature of the protest about the music, how often, for how long; does the music habit interfere with other areas of life (play, school, family life); what happens if you make it so there's no access to the music for a few days. Anything you're concerned about, get some detailed data down so that you're discussing facts rather than perceptions.
There are lists of evaluators at
www.aspergersyndrome.org .
Best,
DeeDee
