Pop/Jazz; Theme and Endless Variation: Jazz at the JVC Festival
LEAD: THE JVC Jazz Festival, which has rumbled into town and is opening its many doors tonight, is half a jazz festival and half a festival about jazz. For every Dizzy Gillespie, who is playing at Carnegie Hall with a big band, there is a group like the Jazz Passengers, who can play jazz but who mostly use it, query it, poke some fun at it and revivify it.
