Dustin Hoffman may be late to the party, making his debut as a director at 75. But the guy’s a natural. It’s Hollywood that’s selling plastics. Hoffman uses all he’s learned as a virtuoso actor to shape a film of flesh-and-blood characters, flushed with humor and tenderness. The defiantly funny and touching Quartet, based on a play by Ronald Harwood (The Dresser), concerns opera musicians living a not-so-vida-loca in a cozy retirement home in the British countryside. Illness isn’t absent, but self-pity is. What shakes up the place is the arrival of prima donna Jean Horton (Maggie Smith, who else?). Tenor Reggie Paget (Tom Courtenay, superb) is horrified. His marriage to Jean was short, his bitterness lasting. There’s some nonsense about the home going under unless Jean and Reggie team up for a benefit concert with contralto Cissy (a poignant Pauline Collins) and baritone Wilf Bond (Billy Connolly, a randy hoot). Not to worry. The actors are world-class charmers, and the magnificent Dame Maggie is the diva divine. Her wit still stings, as it does on Downton Abbey. But Hoffman also has the grace to let cinematographer John De Borman light her simply sitting still, showing a timeless fire and beauty. Hoffman doesn’t wallow in the ravages of age. He celebrates resilience in the face of it. His Quartet makes sweet music that’s irresistible.