Anytime you are playing anything Bill Powel, Nicky Hopkins, Billy Payne, Chuck Level, Roy Bittan etc. You kind of have to go for the style and then the feel. I would go as far as to say that you should listen to what they listened to. Bill Payne said he listened to a lot of New Orleans/ stride playing and loved Professor Longhair. He told me to go back to the source which I'd say 80% of keyboard players I know refuse to do. There is a reason these guys are monster players. Most often they had some kind of formal training or in some cases they were a freak of nature. They also didn't have a lot of technology which is probably a different argument.