ok i get modes. but i saw somethin on joe satriani and he was talking about 'surfing with the alien'. he said he was in G dorian and moved to G major? would the G dorian key be F major?
Yes you're right, it's like you played the Fmajor Scale starting on G. Then the chor is Gm
so he changed keys?
Yes, its a modulation from the verse to the chorus