The year Tony Bennett turns 80, he releases the CD “Duets, An American Classic,” and for Public Broadcasting System, he performs nine duets (eight from the album) and a solo in front of an audience in L.A. Billy Crystal, Catherine Zeta-Jones, Bruce Willis, John Travolta, and Robert De Niro provide brief commentary, and there are a few clips and lots of stills of Bennett through his career. Mostly it’s singing: with Barbra Streisand, John Legend, k.d. lang and Chris Botti, Diana Krall, Juanez, Elton John, Michael Bublé, Stevie Wonder, and Christina Aguilera. The Tony Bennett Dancers give cabaret and 60’s stagings to several numbers.