This is your brain on jazz...

Interesting study scanning the brains of jazz musicians with functional Magnetic Resonance Imaging as they improvise (on a keyboard in this case).

The crux: performance-monitoring regions of their brains shut down and various areas associated with dreaming, with all of the senses and with regulating emotions kick in, in addition to an area involved in organizing self-initiated thoughts and behaviors.

In other words, they stop thinking about what they're doing on a conscious level and just let it come to them, which sounds a lot like Mr. Sonny Rollins describing what happens to him in concert, or Michael Jordan in one of those stretches where he'd hit every shot he tossed up for that matter.