Remember that you might be asked to play ANYTHING they want... it may not seem like a good idea to take a crash course in say... Irish folk music, but what if you get a call? If you can't play it, there goes you're $ and valuable reputation points.... The more good jobs you do, the more referrals you get, and the bigger your name becomes. (I've never worked as a studio musician but I used to play with/work for quite a few).