The Jonah Levin Band
From the movie One Trick Pony (1980). Folk rocker Paul Simon plays (badly) Jonah Levin-- basically himself, if he had never made it big. Levin's big '60s hit was the anti-Nam "Soft Parachutes."
The Jonah Levin Band is played by real-life session vets, and they also play full versions of the songs on the soundtrack album: Steve Gadd on drums as Danny Duggin, Richard Tee on keyboards as Clarence Franklin, Tony Levin on bass as John Dibatista, and Eric Gale in guitar as Lee-Andrew Parker.
The movie also features Tiny Tim, Harry Shearer as his manager, Rip Torn as his studio head... and, in a nice piece of casting against type, minimalist rocker Lou Reed as a producer who loads up Jonah's latest single with strings, horns, and chorus girls and all other kindsa crap (so, basically, Phil Spector). Playing themselves are Sam & Dave, the Lovin' Spoonful, The B-52's, and David Sanborn.