PARIS (NYT NEWS SERVICE).- You’ll find them up in the balcony, or in standing room, silently mouthing the libretto or humming along with the score. These are the superfans: the compulsive lovers of opera or ballet or theater who see every performance; who travel from city to city for Marilyn Horne or Mikhail Baryshnikov; who know every downbeat of “Così Fan Tutte” or “A Chorus Line.”

Most are harmless admirers. Some become lay experts. But the superfan can be conniving, as in “All About Eve,” or even murderous: the Tejano sensation Selena was killed by her fan club president. If great art stimulates the heart and the head, the superfan has the ratio out of whack: Passion wins out over reason, and appreciation tips into obsession.

In the annals of French art history, the superfan par excellence is Edgar Degas: the most Parisian of all the impressionists, and an obsessive of the first magnitude over the opera and ballet. For decades, he watched the leading singers and dancers under the new electric lights, and scrutinized the young members of the corps de ballet in the wings and backstage. Close to half of Degas’ painterly output depicts the Opéra de Paris — which was (and still is) both an opera and a dance company, and which he knew as intimately as Monet knew Giverny’s gardens.

In the year 1885 alone, Degas went 55 times to the still-new Palais Garnier. He saw one opera, the now-forgotten “Sigurd” by Ernest Reyer, at least 37 times. His images of dancers making their grandes arabesques or bending at the barre, now schmaltzy stalwarts of dorm-room posters, were the projects of true mania.

“Degas at the Opéra,” a deep, enlightening, rather perverse exhibition on view here at the Musée d’Orsay through Jan. 19, strips away the sentimentality that has accreted onto Degas’ pictures of dance and music, to reveal the compulsion and single-mindedness that drove their innovations.

It includes more than 200 works in a panoply of media — paintings and pastels, monotypes and painted fans, even solarized photographs of dancers in shocking orange — but only one subject: the hermetic world of Paris music theater, a place of grand spectacle and even grander depravity. The show also features a bronze cast of the tutu-clad “Little Dancer Aged Fourteen,” the only sculpture Degas exhibited in his lifetime; the wax original is in the National Gallery of Art, which will host “Degas at the Opéra” next March. Usually a figure as quaintly perky as Eloise, she has never looked less tender.

It turns out that today’s age of superfandom — wherein the selfie has replaced the autograph, and TV audiences mount petitions against plotlines — has roots in the theatrical milieu of the dawn of industrial capitalism. What Degas demonstrates, and why “Degas at the Opéra” feels so relevant, is that audiences have always held more sway over performers than we admit. Today’s “age of the fan” is not so new, and the opera of 19th-century Paris, in particular, was literally built for adulation and abuse.

Degas cared for music, and had particular admiration for Gluck, but he was not only at the Opéra to listen. In late 19th-century Paris, opera was a social spectacle that made it an ideal subject for a painter of modern life. For both the upper class and the new bourgeoisie, the real point of a night at the theater was to see and be seen. The performances were often stodgy or familiar — particularly the ballets, which by Degas’ time were little more than a sideshow between opera acts. Not a problem: that allowed the audience to ignore the stage and pay attention to the real theater around them.

Degas went as often as he could afford it: first to the Opéra Le Peletier, the company’s home until a fire destroyed it in 1873, and then to the choke-me-to-death-with-gold-and-marble Garnier, which opened in 1875 and which Degas despised. At both houses, he trained his eye on both the stage and the audience, which he painted from unorthodox perspectives — sometimes a sharp view down from the loges onto the dancers’ heads, sometimes a sotto-in-su gaze up from the orchestra seats to the women in the priciest boxes. In pastel, particularly, he could imitate his view of the backlit performers, their faces lost in the footlights.

Not until 1885 could Degas afford the Opéra’s most expensive subscription, which got him a seat every Monday, Wednesday and Friday — and much better privileges than that. Three-day subscribers, principally aristocrats and financiers who, like today, underwrote new productions, got to enter the Garnier through a dedicated entrance. More important, subscribers had the right to pass through a communicating door backstage, even during performances. Back here, the men would come into the dressing rooms of the divas, and proposition the dancers in the “foyer de la danse,” an opulent mirrored chamber that Garnier designed as, basically, a hunting ground. You had to sign in when you entered: At the Orsay we see Degas’ name on the ledger, day after day.

Most of the ballerinas in Degas’ paintings and prints were not the athletic, self-reliant dancers we see on the stage today, but miserable girls from the lower ranks of French society. At midcentury, more than half of the Opéra’s new enrollments were fatherless; their mothers were usually laundresses or concierges, and most girls arrived at the opera house barely fed. There the ballet masters “broke” the girls — stretching their little bodies on racks, reshaping their feet with specially carved boxes. Onstage, or in Degas’ pastels, the girls in their tutus might look angelic. But to the Opéra subscribers these dancers were known as the “petits rats”: little rodents, barely paid, ripe for sexual exploitation.

The distance between the opera and the brothel was vanishingly thin in the late 19th century. For Romantic author Théophile Gautier, the dancers at the Opéra were “frail creatures offered up in sacrifice to the Parisian Minotaur,” who “each year devours virgins by the hundreds, with no Theseus coming to save them.” In Degas’ images, the most devoted operagoers hover in the wings like birds of prey, and even mothers are on hand to pimp their young daughters to the subscribers.

He made that sordor visible in 80 pitch-dark monotypes he made to illustrate a novella by Ludovic Halévy — his good friend, and the co-librettist of “Carmen.” Degas depicts portly men sitting in the Garnier foyer beside dancers who stare into space, or top-hatted aristocrats swarming around the ballerinas like vultures. (New York audiences saw these prints in the Museum of Modern Art’s “Edgar Degas: A Strange New Beauty” in 2016.)

Yet even in Degas’s now beloved, superficially sunnier pastels, the dancers appear more often like possessions than fellow artists. They are working girls, bent over, tying their slippers, slumped in the corner — rarely elegant, and always being watched. Though he admired some female painters (notably Mary Cassatt), Degas was an intense misogynist, and the formal innovations of his art went together with an avaricious focus on control.

“I have perhaps,” he once confessed, “too often considered woman as an animal.”

Little Marie van Goethem, the Belgian-born model for Degas’ statue “Little Dancer Aged Fourteen,” was one of these “petits rats.” She was born in 1865, the second of three girls. Five years later, her father died, and in the same year the Franco-Prussian War broke out. Marie, her sisters, and her laundress-prostitute mother were scrambling across Pigalle. Ballet was the only way out.

At 12, Marie entered the Opéra’s conservatory, and while the dance masters broke her she posed in Degas’ studio for extra money. He sculpted her in fleshy wax at two-thirds life size, her eyes shut tight, her face scrunched up like a wadded rag. Instead of capturing her mid-plié, Degas chose to sculpt her standing in the awkward fourth position, feet perpendicular to the torso and pointing in opposite directions. He gave her a sharp jaw and a forehead like a ski slope. To her body he affixed a real tutu, and real human hair.

If a few avant-garde types appreciated the audacious “Little Dancer” at the impressionist exhibition of 1881, most of the Paris press despised the sculpture. “Why is she so ugly?” wrote the critic for Le Temps. “Monsieur Degas is doubtless a moralist: Perhaps he knows something about the future of dancers that we do not.” A pretty coy remark — for everyone would have known that dancers were a step away from the bordello, and that their careers, even their next meal, were the gift of well-dressed fans.

Have the performing arts really given up on predation? Today’s dancers might not be as desperate (or as young) as little Marie, but the opera and the ballet have always been games of class distinction, and philanthropy has more uses than a tax write-off. I couldn’t help but think, as I made my second pass of “Degas at the Opéra,” of last year’s scandal at the New York City Ballet, in which star dancer Chase Finlay exchanged lewd texts with donors to the company, sending pictures of sex acts and pledging to treat female dancers “like the sluts they are.” (Two other fired dancers have since been reinstated.) The Paris Opéra Ballet has its own problems; last year, a leaked questionnaire revealed that three quarters of the dancers reported suffering or witnessing verbal harassment, and one quarter had endured or seen sexual harassment.

Degas never married. He left no record of any mistress. He may have died a virgin. But just because he kept his hands off Marie and the other “petits rats” does not make his art less creepy. Van Gogh, in a letter as blunt as Finlay’s texts (though tamed in this translation), wrote that Degas “watches human animals stronger than himself getting erections and having sex, and he paints them well, precisely because he doesn’t make such great claims about getting an erection.”

This painter who “didn’t like women,” in van Gogh’s estimation, found at the Opéra an arena of desire and depredation that he could translate into pure form — beautiful and stifling, modern and cold. This is the truth about superfans: they smother what they love.

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