One of the ancient professions, busking had degenerated here to a form of begging by the talentless handicapped before its resurgence in the late 1960s and early '70s. (Campbell states categorically that the renaissance ""began twelve years ago in California,"" but acknowledges that ""New Yorkers might disagree."") Now, organized street performers sign up for time at San Francisco's cable-car turnaround, a prime spot; the Cannery and Ghirardelli Square in that city and Quincy Market in Boston (the first to legalize busking) employ bookers to audition and schedule performers; and the city of New York puts out a guide to local buskers. Campbell, a former YA librarian, toured the country in 1979 and got to know the huskers of San Francisco, New Orleans, New York, and Boston, the four thriving centers. Performers featured here include a violinist who covers Broadway intermissions, taxiing from theater to theater with split-second timing; a pianist who works off a pickup truck at Fisherman's Wharf; a bespectacled expert on ""musical glasses"" who has soloed with the Denver Symphony Orchestra and played his 39 water-filled brandy snifters on the Johnny Carson show; jugglers with flames and knife blades; a ""human juke box""; and a group that bills itself as ""the world's smallest circus--1/4 ring."" Some are would-be actors or musicians waiting for a break; some are scornfully referred to by the pros as Juilliard students earning lunch money; others, whether dropouts from academia or ""crazy all along"" (as one misfit from a family of doctors put it), simply love the life, the art, the response of the crowd, and especially the freedom from straight life and employment. In telling their stories, Campbell proves an alert, responsive listener, with an ear for the music and the patter and an eye for the different cities' quirks. She writes with spirit and style and deserves a hand for her original subject and first-hand research.