From the washed-out images to the twee voice-over (courtesy of director Stephen Walker), this British television documentary about the titular Massachusetts senior citizens' chorus so slavishly embodies the creakiest clichés of British TV documentaries that you begin to wonder if it's all a big put-on. Maybe Christopher Guest directed the damned thing under a pseudonym. Fortunately, Walker's subjects — nearly all in their 80s and 90s, with a greatest-hits collection of medical ailments and a set list that includes the Beatles and Sonic Youth — more than carry the day. Set over the six weeks leading up to the chorus's latest concert, Young at Heart adopts the will-they-pull-it-all-together-by-showtime formula of so many backstage docs, with the caveat that, for these performers, time is not on their side. The film's appeal is both sentimental and perverse: It's not every day that you get to see a 92-year-old woman solo on "Should I Stay or Should I Go" or a deeply affecting rendition of Coldplay's "Fix You" performed by an octogenarian with congestive heart failure. Not surprisingly, a feature remake is already in the works.