Who is the artist on this funk//rock cover of George Gershwin's "Summertime"?

I was recently at a high school rhythm and blues show and one of the songs really caught my ear. The song was credited (both in the show booklet and by the announcer) as George Gershwin's "Summertime," but it didn't sound very much like the original. This version was very funk/jazz, with a distinct guitar riff, a cool b line (being played on electric keyboard), drums that drifted between jazz and rock, and a baritone sax. The saxophone's piece sounded loosely like the original song, but that was about all. I know I've heard the guitar part somewhere before, so I know it wasn't an original arrangement. If somebody could tell me the artist who recorded this arrangement, I would greatly appreciate it.