I find the overall question interesting: how does zapping certain parts of the brain affect behavior and, more specifically, creativity and artistic performance?
But I don't think there's yet any evidence that it does anything very special. If you want a skill, practicing intelligently still seems the best way to go.
It's funny that he was doing a "counting large sums" test; though it appeared in the movie Rain Man, I don't think I've seen any actual non-anecdotal evidence that that's a skill of savants. It does not seem very scientific of him to use something like that for a test.
And in what way do you want to be like Mozart? His talent you can practice and get - nothing special. His fame? Good luck.
I don't think there was anything special genetically, but certainly parentally. Everyone's a genius with enough practice, but it won't guarantee fame.
I definitely don't know about the genetic part (so shouldn't have said it) but I thought is was pretty well established that there is something qualitative, not just quantitative, about the way a genius thinks. I could be wrong; this is certainly not my field.