Is it cruel to enjoy giggling at tone-deaf singers on YouTube or "American Idol," as millions of people apparently do? Perhaps. But there's also something uniquely amusing and trainwreck-compelling about bad singing, particularly when it's done with sterling conviction.

Florence Foster Jenkins knew that — or, at least, benefited from it — long before the digital era. For decades, the wealthy New York socialite and patron of the arts performed regular concerts for carefully handpicked audiences, who applauded her painfully flat renditions of difficult arias by Mozart, Verdi and others. Her Melotone recordings lived on after her 1944 death in reissues with waggish titles like Murder on the High Cs.

Was Jenkins genuinely deluded about her abilities or so eager for the spotlight that she didn't care who laughed behind her back? Either way, this is a great role for an actor of undisputed talents such as Meryl Streep. She plays Jenkins in this loose dramatization of the last year of the diva's life, directed by prestige-film stalwart Stephen Frears (The Queen, Philomena). It's a broad, entertaining performance — all frothy dresses and trilling, operatic mannerisms — that anchors a serviceable film about the age-old problem of what happens when ambition exceeds ability.

Nicholas Martin's screenplay appears to take the position that Jenkins had little to no self-awareness. Hence it falls to her common-law husband, the washed-up actor St. Clair Bayfield (Hugh Grant), to shield her delusions from the titters of the mob. This he does assiduously, paying off critics and catering to Florence's every whim, even as he secretly maintains a younger girlfriend (Rebecca Ferguson) on the side.

Watching these eccentric domestic arrangements play out is good fun, especially when Florence decides to add a new accompanist to the mix. As Cosmé McMoon, the only pianist not too "aggressive" for Florence's taste, Simon Helberg is the film's breakout star. A poor kid seeking his big break, McMoon has clearly honed his skills as a simpering sycophant, but Jenkins' singing tests even his powers of toadyism. Watching him struggle to heap praise on her is a delight.

As the film goes on and Jenkins prepares for her famous concert at Carnegie Hall — her first and only vocal performance that was open to the unforgiving public — she and McMoon develop a touching rapport. Further exploration of that relationship might have helped bring more insight and nuance to Jenkins' character. Instead, however, the script keeps returning to the travails of Bayfield — an intriguing personality, but not the strongest protagonist for the story, given that the inevitable focus of our attention is Jenkins herself.

One of many semifictionalized takes on this bizarre story (including the recent French film Marguerite), Frears' film tries to have its cake and eat it, too. We're encouraged to laugh at Streep's earsplitting re-creations of Jenkins; then we're nudged to admire the songstress for her indomitable determination, and to shed a tear for Bayfield and his devotion to her dream. There's a bit too much special pleading, as the script repeatedly reminds us that Jenkins' generous patronage helped support true talents like Enrico Caruso.

Would it have been merciful, perhaps, if someone had told Jenkins that the emperor had no clothes before she had to read it in a review? That question isn't broached here. Still, this cozy chamber drama of a film is generally low-key enough to let us draw our own conclusions about whether a dream based on delusion is better than no dream at all.

Like those terrible online singers who perform with all the swagger of Beyoncé, Streep's Jenkins invites mockery but also marvelment. Perhaps she makes us a bit ashamed that most of us are too smart — or too scared — to jump up onstage and proclaim ourselves artists, with or without the world's support.