Frank Zappa and the Mothers of Invention jamming at a rehearsal in 1973. Great lineup. Frank Zappa on lead guitar, Jean-Luc Ponty on electric violin, Ian Underwood on clarinet (or is that an english horn? oboe?), George Duke on clavinet. ... Frank Zappa Mothers of Invention George Duke Jean Luc Jean-Luc Ponty Ian Underwood Electric Violin Clavinet Clavi Oboe English Horn Clarinet Woodwinds Woodwind Rehearsal