I have a belief that the brain is like a computer. It stores memories and the instructions on how to function properly upon doing every day things. There is only a limited amount of space with which to keep this information.
In a savant, these "instructions on preforming everyday tasks" aren't able to be stored properly for some reason or another and as a result, there is a bunch of available space that is free to be occupied by certain behavior or task, such as the ability to play the piano. This huge amount of free space allows such a task to be done at a much more efficient level than an average person, who's brain is full of the "everyday task" knowledge.
Anyways, that's just a small little observation I've had. Just wanted to share it.