Charles Limb, I've heard speak via a TEDtalk on hearing and listening (see below.) Dr. Limb has been researching what improvisation and musical creativity does to your brain. What a cool subject matter! TTBOOK interviewed him and the jazz musician, Mike Pope, in their series on The Creative Brain.
I can totally relate to what Charles and Mike are saying here. Having done significant improvsation in the folk/pop/rock world, the parts of my brain required to move (I can feel it!) have become almost innate and totally natural. I can be thinking about non-musical things and at the same time be creating music I've never created before.
A couple weeks ago, I improvised (live! yikes.) to my friend, Shenandoah Davis' beautiful music. And although her songs fit in the genre of singer/songwriter, they do not fit in the genre of folk/pop, well, at least not on an improvisational level. This is part of why I love her music so much. After the show was over, I mentioned to her how much I enjoyed playing with her so much - I could literally feel my brain doing something differently. It's a pretty cool... and kind of a bizarre sensation.