'Florence Foster Jenkins' sings, even though she can't (PG-13)

“Florence Foster Jenkins” is a one-joke movie, but it’s a pretty good joke, and the fact that it’s based on a true story only makes the gag more delicious. Directed by Stephen Frears (“Philomena,” “The Queen,” “High Fidelity”), the film focuses on the wealthy New York socialite who dreamed of being an opera star and gave concerts for adoring fans all around the city. The only problem? She simply couldn’t sing.

Florence, as played by Meryl Streep — and really, you have to believe this slight film got made only because Streep’s name was attached — is clueless about her lack of talent. She founded the Verdi Club, famous for its artistic tableaux (in which Florence plays a starring role), but she longs for a bigger spotlight. She faithfully takes voice lessons from sycophants who lie to her because they’re paid, aided and abetted in her quest by her younger husband, St. Clair Bayfield (Hugh Grant), who is also well taken care of courtesy of Florence’s bank account.

A failed actor, St. Clair is well aware of her limitations, but one of the script’s sweeter conceits is that though he has a young mistress (Rebecca Ferguson), he has genuine affection for Florence. He’s something of a benevolent parasite who cares for her when her health grows precarious and protects her from critics who won’t be bribed and might dare to write the truth about her performances (not as many as you might imagine).

He is also the soother of nerves less steely than his own, namely those belonging to Cosme McMoon (Simon Helberg of “The Big Bang Theory”), the gentle pianist who auditions to become Florence’s accompanist and accepts the job without knowing what he’s gotten himself into. Helberg, who credits Streep for raising the bar for his performance, is wonderful: His face, when Cosme first hears Florence sing, is a morass of shock and disbelief that slowly dissolves into twitches and tics, settling into a stunned horror. He’s a nice guy, Cosme, but does he really want to risk his own reputation to help a rich lady buy her way to fame? 

The story, as thin as Florence’s comprehension of pitch and tone, builds to a possible concert at Carnegie Hall. Will the audience, bigger and less controlled than the salongoers who usually see her, accept Florence or howl with laughter? It’s not much of a foundation for a film, but Streep evokes empathy for Florence, whose past hasn’t always been as easy as you might think. With her performance and Frears’ sharp eye for detail, this odd little film turns out to be a pleasant diversion — unlike Florence’s concerts.

Cast: Meryl Streep, Hugh Grant, Simon Helberg.

Director: Stephen Frears.

Screenwriter: Nicholas Martin.

A Paramount Pictures release. Running time: 110 minutes. Brief suggestive material. Playing at O Cinema Miami Beach and area theaters.