There are people at the extremes who aren't able to do anything musically, and then others sort of fall in the middle. And the same thing with math, and the same thing with art. You'll find people who are geniuses, or prodigies at the far end of the bell shaped curve, and I think you will find some of the acquired savants in that category who happened to have been endowed with that kind of talent, which explains why not everyone becomes an acquired savant.