BBC NEWS | Science/Nature | Musicians have ‘more grey matter’
Professional musicians have more grey matter in a part of the brain involved in processing music, scientists have found. The discovery could explain why musical virtuosos tend to be born not made.

But it is unlikely to resolve the long-running debate about what makes a potential Mozart. Repeated flexing of the brain by practicing a musical instrument could account for the extra grey matter in the auditory cortex.

And this quote:

There must be a great influence of genetics to account for the great volume of grey matter in the professional musicians – Dr Peter Schneider

I am not a neurological expert, but I can observe myself and my development. The brain is no different from any other part of our body in the sense that it can be trained. When you play baseball you will develop a strong throwing arm, when you play Go or Chess you will develop whatever part of the brain that supports those games, and when you play an instrument for years you will develop both the physical movement aspect and the part of the brain that supports music. It’s nature AND nurture – Wikipedia Link to the Nature vs Nurture debate. It’s a silly debate. Some have lots of talent, but no application. Others have no talent, but strong discipline and desire. They will grow their musical grey matter through their work. And once in a while we come across people with great talent, discipline and desire. And, to make the circle complete, of course there are people with neither talent for music nor the discipline and desire to develop that art.

In The Integral Vision, Ken Wilber defines “Quadrant Absolutism” nicely:
Extreme Idealism (I): Mind is reality
Extreme Scientism (IT): Matter is reality
Extreme Postmodernism (WE): Culturally-constructed meaning is reality
Extreme Systems Theory (ITS): The Web of life is reality

Correct answer? All of the above.