Well not knowing a whole lot about the new music industry ... it sounds like you are building "yet another one" sort of site.
What is going to make yours differenet, what is going to make yours unique?
Really given your second point what you want is vast amount of new contribution to 1 so that your site becomes the obvious choice for 2.
If thats the case you want to build a community of contributors of 1 (or use a license which says its free unless you fall into the 2 catagory).
So, if you can get a bunch of musicians to contribute their songs under that license which may end them up with an advert to TV show using their work then you could really have something.
Especaily if you enable artists to be features and then they can self promote on other sites using a feed from your site (like and RSS feed that can push out to Facebook every time you release a new track) and so it automatically distrbutes them ... with links back to the source being your site.
Additional bit: the money.
Your real money would come from targeted advertising or the like. You would advertise your site as you will only take 10% (or something) when they are used by a cat 2 prospect. Your cashflow would come from volume traffic to the site.
Also ... allow a way of having people easily say "I sampled from this one over here" so that you can start to track the chain of usage ... then you have a rule of your site that a percentage (say 20%) of royalties should be split amoungst the various samples to make it fair.