It's probably his way of enjoying the music physically. It likely keeps his other senses stimulated too. A lot of musicians do it, although not as much.
Edit:
Being blind his brain works different. The part of his brain that should have been used for sight is now being used for hearing. He has Very good hearing because of being blind. When sound waves from his voice or piano for instance, bounce off objects around him it let him see things with his ears. So just like bats Stevie Wonder has a sort of echo location ability. When he moves his head around it lets him triangulate the position sounds are coming from. Its as simple as that.
Stevie Wonder goes by "Little Stevie" Wonder.
Stevie Wonder is blind.
Stevie Wonder.
Stevie Wonder is blind.
Stevie Wonder is alive and well!
Stevie Wonder goes by "Little Stevie" Wonder.
Stevie Wonder
No, Stevie Wonder is not single.
No Stevie Wonder is a black.
Stevie Wonder is blind.
Stevie Wonder.
Stevie Wonder is blind.
Obviously Lady Gaga, who even is Stevie Wonder?
Charter traits for Stevie Wonder What can I find for it. I have to know about the Stevie Wonder black amarican.
Stevie Wonder
no its stevland judkins
Stevie Wonder is alive and well!