For anyone deeply rooted in rock music, the first keyboardist that comes to mind should be Ray Manzarek. I have mixed feelings about The Doors, which I'll simplify by saying that their best songs are covers ("Back Door Man," "Alabama Song.") But Manzarek's use of keyboards in was unprecedented in rock & roll, as both the lead instrument ("Light My Fire," "Touch Me") and the bass ("Riders on the Storm," "Peace Frog") in The Doors' most enduring songs. People were drawn in by Jim Morrison, but Ray Manzarek is the reason they kept listening.
Less discussed is Manzarek's influence on art-punk pioneers X, the L.A. quartet whose classic first four albums were all produced by him. Remember Ray Manzarek today with a touching video of him explaining why a future Rock Hall of Famer took a chance on an unknown indie band with obscene tattoos, and stick around to watch him join X for a punk rock sprint through the Doors' "Soul Kitchen."