Talking heads. A look at the art of ventriloquists. The first half examines basic issues, such as establishing two clear personalities for “vent” and dummy, the importance of not moving lips, the range of comedy that’s possible, and the doors that opened when Jay Johnson appeared on “Soap” with his dummy. Several contemporary entertainers and historians comment. The second half profiles the best known ventriloquists — Paul Winchell, Senor WeÃ±ces, Edger Bergen, and Jimmy Nelson – and assesses their strengths. The film closes with an assessment of ventriloquism’s future. Included are many clips of performances.