Packing dozens of artistic egos into one elegant retirement home would seem a recipe for discontent, if not disaster. But at Beecham House in the pastoral English countryside, where professional classical musicians go to play their codas, the residents are more or less genteel and congenial — until diva Jean Horton (Maggie Smith) arrives to upset a few teacarts.

Jean used to sing in a quartet with three of Beecham’s residents, including her ex-husband, Reggie (Tom Courtenay). She broke up the group, and her marriage, when she went on to a star solo career.

Now that she’s moved in, other residents conspire to reunite the foursome in time to perform the quartet from “Rigoletto” at the home’s annual musical fundraiser.

“Quartet” seems a surprising choice for Dustin Hoffman’s directorial debut. For one thing, it’s so veddy British that you expect Smith to suddenly morph into the tart-tongued Dowager Countess she plays on “Downton Abbey.” For another, going by the history of his roles as Ratso Rizzo (“Midnight Cowboy”), Tootsie (“Tootsie”) and Papa Focker (“Meet the Fockers”), the only quality the 75-year-old Hoffman shares with these characters is age.

Whatever his imprint on the film might be, it’s overshadowed by the performances of its stellar, veteran cast, to whom Hoffman wisely gives ample rein.

Courtenay quietly stands out for his subtle portrayal of bitter, taciturn Reggie. Billy Connolly, despite playing a rogue ostensibly made more raffish by a stroke, tones down the ham just enough to be delightful. Pauline Collins (best known in the United States for “Shirley Valentine”) brings the right touch of bewilderment to Cissy, whose exuberance can’t hide the onset of dementia.

Michael Gambon, as a retired director who has no intention of putting his domineering personality out to pasture, is a treat every time he sashays on the scene in outlandish silk robes.

As outwardly imperious but inwardly wobbly Jean, Smith reveals a fear of aging compounded by knowing her once-great voice is also getting creaky, and that loneliness hits hardest for those used to being universally adored.

As supporting players, most of the home’s other elderly residents are musicians in real life. They provide bonus performances that both offset and blend in with a decidedly leisurely pace.

Ronald Harwood wrote the screenplay, basing it on his 1999 play. Harwood has been nominated for an Oscar three times, winning for adapted screenplay for “The Pianist.”

He also wrote the titular role for “The Dresser” that Courtenay made famous on stage and screen in the early 1980s, and the two men are clearly simpatico. This time out, Harwood forgoes plumbing emotions to gasp-worthy depths in favor of a lighter touch, but Reggie’s pain is palpable, bringing on the film’s most poignant moments, with Cissy’s struggles with forgetfulness a close second.

At times, “Quartet” seems like no more than an installment of “Masterpiece Theater” with an A-list cast. It rolls along like the gently sloping hills surrounding Beecham House, never in a hurry to get anywhere.

But then, it doesn’t need to be. It’s a sweet little parlor piece with no symphonic pretensions.