The problem with having a whole lot of domain names, is that to promote them to rank well in search engines will mean getting links to all of them --- as directories and most sites won't link to all of them for you, you then have to spread it around, so end up with a whole lot of average or mediocre ranking sites - you are better off focusing that effort and getting all the anchor text links to one domain (and deeper links into that site) and get that ranking really well.

Re keywords.. if you go to the overture tool and tpye in 'music downloads', you get these suggestions:
You may be better off targeting and ranking well on on some of these 3 or 4 word phrases.

CBP