When Meryl Streep steps from her limousine onto the red carpet in London’s Leicester Square, everything about her comportment—as she strikes poses with castmates Hugh Grant and Simon Helberg, greets fans along the stanchions and hugs past co-stars like Stanley Tucci who’ve turned out for her—announces that she’s been here before. “It’s quite a scene, isn’t it?” she later says about the glittery film premiere. “It doesn’t get old. I mean, who gets to see a movie with 1,600 people?”

With her hair in an elegant but simple updo, Streep confidently strides the red carpet in a black silk jumpsuit, heeled ankle boots and a long, beaded statement necklace. As she reaches the entrance to the theater, the emcee for the event introduces the star of Florence Foster Jenkins to a cheering crowd. He then asks her, “We know you can sing, because we heard you sing in Mamma Mia. So how difficult is it to sing badly?”

Streep does not hit a false note at the premiere—until the film rolls. Inside the theater, the crowd watches as the actress appears on-screen bedecked in jewels, fur and a tiara as Florence Foster Jenkins, an eccentric socialite who fancied herself an opera singer and whose peculiar career culminated in a legendary 1944 performance at Carnegie Hall that sold out within two hours.

When I sit down with Streep and the film’s director, Stephen Frears, later at a photo studio in London’s Camden Town, Streep describes Jenkins’s pursuit of her dream in noble, artistic terms. “There’s that great Vincent van Gogh quote: ‘I am seeking, I am striving, I am in it with all my heart.’ That’s the aspiration.” The self-styled soprano had another thing in common with the Dutch painter: She famously lacked an ear. (She also lacked rhythm, tone and any self-awareness about her singing ability.) History remembers Jenkins’s screeching, caterwauling voice in superlative terms: “the world’s worst singer.” Even so, many who snickered or guffawed upon hearing Jenkins would come around to applaud her. “She seems to have known the pleasure people got,” Frears says of Jenkins. “There was laughter, and she seems not to have minded.”

Jenkins was born in 1868, in Wilkes-Barre, Pennsylvania, to a family of means—her father made his fortune in railroads and banking. Forbidden from pursuing a career in music by her father, she rebelled, eloping with Dr. Frank Thornton Jenkins. The union didn’t last long, but its aftereffects—he gave her syphilis—colored the rest of her life. In 1909, the same year Jenkins’s father died and she came into her inheritance, she met St. Clair Bayfield, a Shakespearean actor from England who became her common-law husband as well as her publicist and manager. Jenkins launched her singing career in her 40s, using her wealth to underwrite her passion.

“She had this need for attention,” says Donald Collup, who wrote and produced the 2008 documentary Florence Foster Jenkins: A World of Her Own. “She had to be the focus.” This was true as she staged, with Bayfield’s help, a series of recitals—many under the auspices of the Verdi Club, a private organization she founded—that became must-see events for New York society. According to a newspaper clipping about one of Jenkins’s 1934 performances, “The audience, as Mrs. Jenkins’ audiences invariably do, behaved very badly. In the back of the hall men and women in full evening dress made no attempt to control their laughter.” Jenkins’s performances were, according to Collup, akin to “the first rounds of American Idol, where performers who have no business singing get up and think they’re great and make fools of themselves. The general public always watches those rounds—because they’re funny.”

In the decades following her death one month after the concert, Jenkins amassed a cult following (among her admirers: Barbra Streisand and David Bowie). Jenkins’s performance remains one of the most requested from the concert hall’s archives—except it was never recorded. “You get asked about Benny Goodman, the Beatles, Judy Garland—Florence is right up there with them,” says Gino Francesconi, director of the Archives and Rose Museum at Carnegie Hall. “All the things she did in her life led up to this. She was 76 and making her Carnegie Hall debut. Why didn’t she record or photograph the concert? It’s so odd.”

It’s easy to see Jenkins’s need to perform as an expression of her ego, or even narcissism (her given name was Narcissa Florence Foster). Too easy, according to Streep, who views Jenkins as deeply insecure, not simply overcome with delusions of grandeur—though she grants the latter might be part of Jenkins’s appeal. “It’s also our prurient interest in other people’s vanity,” Streep says, “imagining that it has nothing to do with our own.”

As played by Streep, Jenkins is driven by a force more powerful than vanity, as if her entire life—simultaneously privileged and tragic, with the specter of death a constant companion—was animated by the joy of singing. “Her personal challenges,” Streep says of her alter ego, “what was stalking her in her life, made her make a decision to live every second deeply, intensely and to her joy.”

That, in turn, drove Streep’s decision to make this movie: “To choose the one that chooses joy—and there are a lot of reasons to go and to explore the endless dystopian vortex into nihilism—is saying, ‘Music matters, love matters.’ What’s the value in being alive right now? It’s saying, ‘There is value.’ That’s in there.”

And in some ways the film ultimately functions as an expression of Streep’s outlook on life and art—the spiritual child of Mamma Mia and The Hours, and the apotheosis of The Devil Wears Prada star’s devil-may-care period. It’s telling that Streep calls Florence Foster Jenkins “one of the most fun things I’ve ever done, without question,” and makes no excuses about having chosen the project simply because it would be enjoyable. “Seems like a pretty damn good reason.”

When I ask the 67-year-old actress if she enjoyed the London premiere, she nods eagerly and lights up. “It’s really nice to hear a whole place just rollicking, isn’t it?

“I talked to Stanley,” Streep says of her friend and former co-star Stanley Tucci. “He brought the teenagers, and they loved it—that’s even more important than what Stanley thought, frankly.”

As pleased as she is that Jenkins’s story resonates with young people, Streep is also somewhat incredulous at her own status as social-media meme. “I don’t even know what that means,” Streep says with a laugh. She is at a loss as to how to explain Taste of Streep, a buzzy Instagram account that features image after image of the actress emerging from or melded into various foods. “People have too much time on their hands,” she says. “We need to create more jobs!”

And yet Streep recognizes the power of more curious forms of entertainment—whether in wildly off-key singing or her own face Photoshopped onto fast food. She throws her arms up and laughs loudly at the absurdity. “My head is coming out of a chimichanga. Can you imagine?”

Although Florence Foster Jenkins is Streep and Frears’s first film together, they already knew each other socially, and when Frears called to say he had a script for her, Streep signed on without even reading it. The trust carried over to filming, as Frears rarely gave his star notes. When he did, Frears delivered them with great care. “If you’re stupid, she’ll let you know,” he says.

“I’m a diva—is that what you’re saying?” she says with a laugh. Later she adds, “You would just look at me like”—she raises an eyebrow—“and I would say, ‘OK, I’ll do it again, I’ll do it again. Let me do it again, let me do it again.’ ”

During production, which took place in the U.K., Frears would invoke a well-known film-world witticism: “We’re making a movie together—let’s hope it’s the same one.” As it turned out, they discovered they had a simple, shared vision: to entertain.

“I thought this would give pleasure,” says Frears.

“I put that high on the list,” says Streep.

Much of that relied on pacing, says Frears. “This film depends on lightness—like a soufflé.”

Despite wrestling with some weighty themes, the creation achieves the desired lift. “We actually talked about how it was somewhere between Chekhov and the Marx Brothers,” says Helberg, who plays Jenkins’s young piano accompanist, Cosmé McMoon. It’s through his eyes that our view of Jenkins evolves from that of a deluded warbler to something deeper, more sympathetic. As her accompanist, he shares an intimate connection with Jenkins, supporting her through her cringe-worthy yet oddly compelling concerts.

“There was this beautiful relationship that you can find in the music, in the transcriptions, too,” Helberg says. “You’d hear him pause because she forgot the lyric or give her a note that she forgot, or she’d skip a bar and he’d compensate or he’d change keys because she couldn’t hit the last note.”

In one particularly poignant scene, Jenkins visits McMoon’s apartment and they play a Chopin prelude together, he with his left hand, she with her right. As badly as she sings, Jenkins was a piano prodigy as a child. But the ravages of syphilis and mercury poisoning—used to treat the disease—withered her left arm and ended any hopes of a career as a concert pianist.

After they wrapped that emotionally taxing scene, Helberg recalls saying, “Here’s to giving up.” Streep corrected him: “No, no, no. Here’s to giving in.” It was a koan about life in the guise of acting advice that her co-star took to heart. “I thought, Oh, that’s what it is,” Helberg recalls, “giving in to these doubts and these fears that everybody has, including the person considered the best actor ever to live.”

While Streep, who has racked up a record 19 Academy Award acting nominations, receives such praise with grace, when she says she is merely happy to be acting she is not simply being modest. “On a certain level you don’t have any choice—you’re unhappy if you’re not doing it, so you’re compelled in a certain way. And if you’re lucky you can keep working,” she says. “But everybody has troughs and dismal times—every single person. I remember as I was hovering around 40, I thought each movie would be my last, really. And all the evidence of other 40-year-old women at that time—this is 27 years ago—would lead you to believe it was over.”

Those anxieties help explain why Streep is pleased to be as prolific as at any time in her nearly 40-year film career. But they also remind us that her later success was not preordained. Streep points to a number of other impressive actresses who are her peers, but many of them followed her lead after she shattered the glass ceiling for over-40 actresses. Since that milestone, Streep has been nominated for an Oscar 11 times—far more than any actor at that age or during that time (the most any other actor has received is 12).

“She’s an enigma to most people, obviously,” the Big Bang Theory star continues. “She’s also so highly revered that it was impossible for me to even imagine being in a room with her. As soon as I was, she kind of called that out. It’s like she comes into the room and takes her crown off and puts it on you—which she actually did with my daughter.”

In London, while recording the notoriously challenging Queen of the Night aria from The Magic Flute, Helberg brought his 3-year-old to the studio. “Addie had seen some of these clips from Mamma Mia, so she’s very excited and calling for Mewylstreet, Mewylstreet,” Helberg recalls. “Meryl came in wearing a tiara Florence had worn when she had performed, and she sat down on the floor so she could be eye to eye with my daughter. She took off her tiara, put it onto Addie and said, ‘Hello. I’m Meryl Streep.’ ”

Fidelity is a theme woven through Florence Foster Jenkins. Outwardly, there’s the faithfulness and the devotion of Bayfield (who also keeps a mistress at a pied-à-terre paid for by Jenkins) and the hard-won loyalty of Helberg’s McMoon (who at first is mortified by the prospect of performing in public with her). To be true to her, they had to be untrue—telling white lies and perpetuating deceptions to preserve Jenkins’s self-regard. The same went for the music. “To get it just perfectly wrong was very challenging. You have to get to right first, and then you have to hit it with a hammer,” says Helberg, who is a trained jazz pianist.

“My biggest anxiety was that I couldn’t sing as high as she did,” Streep says. “She hit an F above high C. Do you know how high that is? It’s just insane.” Authenticity was paramount for Streep, who tried to match Jenkins note for gloriously awful note. “Florence sang in a particular way—I mean, the way she went wrong was particular to her. It didn’t really have rhyme or reason to it.”

The degree of verisimilitude Streep achieved is impressive, even to a Jenkins scholar like Collup. “It’s a carbon copy,” the documentarian says. “The tonal quality of her singing, the bad diction, the wavering pitch, the attempt to sing high notes and just not really making it—it’s uncanny.”

As Streep took to the task of simulating the world’s worst singer, the rigors of rehearsal and recording took their toll. “A real person, a real diva, doesn’t sing the Queen of the Night more than twice a week, ever,” she says. “And I was going to sing it three or four times a day. That was very hard. I actually lost my voice.”

We have gotten accustomed to seeing Streep’s love of song play out on-screen. There is her musical movie oeuvre—Mamma Mia, Into the Woods, Ricki and the Flash—and, all told, Streep sings in 10 films. But opera is a different discipline altogether.

Streep knows this better than most—and not just from playing Jenkins. At 12, she began studying voice with Estelle Liebling, who trained Beverly Sills when she was still a rising star, as well as many other sopranos with the Metropolitan Opera. Streep traveled to New York each Saturday from her home in northern New Jersey and labored for four years in Liebling’s studio, close to Carnegie Hall, initially with the hope of joining a company, possibly even the Met. Having seen Sills perform, however, Streep eventually realized that, despite having a lovely voice, she wasn’t good enough to be a professional diva. And though she sang plenty, Streep left her dreams of singing opera behind. Until Florence Foster Jenkins.

“Yeah, there were moments when you’d say, ‘Sing worse,’ ” Streep says to Frears.

“You were quite close,” Frears responds, referring to Jenkins’s idiosyncratic intonation.

As Streep pauses in appreciation, I’m reminded of a moment late in the film. Stripped of her wildly outlandish attire, Jenkins delivers a line that resounds like a credo: “They may say I can’t sing, but they can never say I didn’t sing.” This may be true for Streep, who like Jenkins is striving with all her heart, though she holds herself to a higher standard: her own.

“At the end, I sort of thought, Well, that was good,” Streep says, nodding. “I thought I’d done well, sounded good.” She pauses and adds with a laugh: “I also thought I looked good. Someone should have told me!”