If you're referring to the "Plastic Ono Band" with which she recorded her eponymous 1970 album, it was Lennon on guitar, Klaus Voorman on bass, and Ringo on drums. A fantastic record with some of the best recorded instrumental performances by all concerned.
There's also a track on it that she did with Ornette Coleman's group, who at the time were Ornette (on trumpet!), David Izenzon and Charlie Haden on basses, and Ed Blackwell on drums .
― Nom De Plume (Nom De Plume), Saturday, 17 April 2004 17:24 (twenty-two years ago)