I was wondering about this and I just looked it up.
Page 81 of this study explains a little about the possibility of musicians being ambidextrous
http://books.google.com/books?id=juk1xMPqYBsC&pg=PA81&lpg=PA81&dq=Musicians+ambidextrous&source=web&ots=ETRgIm62Kt&sig=Sg7tBqHS20f9jkryuzmKtSGcI1o&hl=en&sa=X&oi=book_result&resnum=4&ct=result