I live in Portland, OR which is about 3-31/2 hrs from Seattle. Seattle is bigger than Portland but it's also more expensive. Seattle would be a great place for musicians (there are also people who play music on the street near the market area). I also know that Portland is really focused on the arts and might be an even better choice. Like I said, it's smaller than Seattle but also cheaper. So maybe you might want to look at both places
Go to this website to compare the costs of living:
Cost of Living - Cost of Living Calculator from CNNMoney.com
Hope this helps!