The general comedic premise behind the new biopic of 1940s New York City socialite Florence Foster Jenkins is that this sweet but delusional woman thinks she can sing, but really produces the dulcet tones of a bleating car horn outside your apartment at midnight.

And it’s a joke that’s played perfectly in the film, starring Meryl Streep as the dowdy real-life figure. Though the really fascinating aspect of the movie is the behind-the-scenes machinations that keep this kind soul from knowing her reality.

Florence, a rich heiress, has an intense love of music — she has an emotional experience watching the great soprano Lily Pons perform. Once a talented pianist, Florence is now too injured to play. So instead she focuses on a singing career.

Hugh Grant plays her husband, St. Clair Bayfield, a mediocre actor with a girlfriend on the side, who is at the center of a grand coverup to keep Florence from embarrassment.

For her concerts, he pays off journalists for good reviews and makes sure only people who are polite to his cause are in the audience.

Joining them in the ruse is Cosme McMoon (Simon Helberg), a piano player struggling to balance working for the lady paying him big bucks and trying to maintain credibility in the music field.

Their struggle is only amplified when Florence decides to book Carnegie Hall and offer free tickets to soldiers who won’t be vetted for friendliness or paid to cheer.

It should be no surprise that Streep is quite good in “Florence Foster Jenkins.” She plays the character well, filling her with fun eccentricities and an endearing quality. It’s easy to see why St. Clair and Cosme go to such lengths to shelter her.

Sure, you’ll laugh at her in the film when she happily belts out yet another off-key note, but soon enough she’ll grow on you, too.