"Of All the undiscovered musicians in the world, how many percent of them(or us) will be heard on MTV or a local radio staion?"
About the same percentage of Artists who get their paintings into an art gallery, the same percentage of golfers who get to play in the Open, the same percentage of lottery ticket holders who get to win a prize, the same percentage of Democratic nominees for President who get to sit in the Whitehouse! etc...
I guess you're really saying why can't MTV and radio play more diverse artists? It's not about diversity, its about advertising selling lots of units froduced by large multinationals. They do not exist for altruistic reasons.
For diversity come to the internet and search for music here. One day they will totaly control it and we'll be back to square one, but for now its open season for independent 'undiscovered' musicians so make hay while the sun shines!