“Act your age” is an injunction that certainly doesn’t apply to the old folks who make up the Northampton, Massachusetts chorus that’s profiled in “Young@Heart,” Stephen Walker’s charming, exuberant and poignant documentary. The group consists of seniors with an average age of eighty who sing songs of more recent vintage—rock ’roll standards that deliberately upend the repertoire you might expect of them—and the film follows them over a six-week period as they prepare, under the tutelage of their caring but demanding conductor Bob Cilman, for their annual hometown concert. (The chorus regularly tours in Europe, but the focus here is kept local.)

Walker hews to fairly conventional norms in presenting the group. Narrating the piece himself with enthusiasm, he offers chronological rehearsal segments, showing how Cilman introduces new material, selects soloists for each piece, and firmly but patiently builds the performances. Interspersed with these he presents more detailed treatments of a few of the chorus members, interviewing them while following their efforts to master lyrics and rhythms that they frequently find a trial. And he takes a detour to cover the group’s performance before a bunch of inmates at a local jail before ending with coverage of the concert for which they’ve been prepping, and an even further one by inserting a couple of MTV-style music videos in which the performers strut their stuff.

Your first inclination about the film might be to apply the old saw that one might be surprised that the choristers could succeed at what they do at all, let alone do it well. But as it continues, any lingering condescension dissipates in the face of the joie de vivre that mark the group’s attitudes and performances. You can’t help but be as taken as Walker is by feisty Eileen Hall, who opens the movie with a rendition of “Should I Stay or Should I Go?” that’s at once startling and moving; and Fred Knittle, an ex-star of the group now hobbled by heart disease and raconteur par excellence, who returns for one last concert and delivers a stirring rendition of “Fix You”; and Steve Martin, a randy jokester with boundless energy.

Of course, with folks of this age group, illness and even death are almost inevitable occurrences, and Walker doesn’t shy away from them when they intrude. It’s impossible not to be touched by Joe Benoit, one of the chorus’ stars, whose legendary memory for lyrics is undimmed even when the effects of his cancer and chemo treatments recur; or the frail Bob Salvini, who returns after a long absence and struggles against illness to sing a duet with an old friend.

There are places in “Young@Heart,” to be sure, when Walker gilds the lily, so to speak, playing his emotional cards with a zeal that can occasionally seem excessive. With a subject like this, the heavier the hand, the less effective it is.

But for the most part he avoids the obvious pitfalls. Even when he goes a bit too far, the choristers themselves anchor the film with their refusal to give up or give in. And Cilman’s combination of down-to-earth common sense and obvious affection and concern for his singers enriches it as well. His attitude mirrors what your reaction to the picture is likely to be. You’ll find it both sweet and sad, uplifting but honest too. And you’ll probably come out of it with a spring in your step, feeling a few decades younger yourself.