Huh, Costanza (mainstream) and Epps (surf-rock) were both self-taught after a brief encounter with the 'real deal.' I'm trying to think of their Anglo-folkie opposite(s) and I got nothing. I think maybe that side of it was more pop fad amongst the fan base with the usual mass-media overexposure to go with.

Costanza is the only 'serious' musician that comes to mind. Orson Wells' "A Touch of Evil" with the Mancini-Costanza score is one of the great opening long-takes in cinema. He's still vivito y coleando at 96 too:

http://www.sandiegouniontribune.com/news/2015/nov/14/jack-costanzo-dizzys-jazz-profile/