Not long ago, a tattoo shop in Brooklyn got a bad review on Yelp. A customer was angry — not about his new ink, but about the soundtrack that accompanied his trip there.

“Why are you playing Sade,” he wrote, inserting an expletive. This was music he found fit for “a plastic surgeon’s waiting room,” not a cool tattoo parlor.

One can sort of understand where he was coming from.

Before record stores neared extinction, Sade was often stocked in the easy listening section. The band’s breakout success in the 1980s owed much to the advent of adult contemporary radio, where huge hits like “Smooth Operator” and “The Sweetest Taboo” eventually got sandwiched between selections from Michael Bolton and Kenny G.

But then and now, Sade had an appeal that lifted it far above the slush pile of schlock.

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The band’s trench-coat-favoring Nigerian-born frontwoman, Helen Adu, known to the world just as Sade, is more responsible for the popularizing of gold hoop earrings than an entire industry of jewelry executives. She did not so much wear polka dots as single-handedly rescue them from the dustbin of Upper West Side frumpiness.

As a generation turned, house D.J.s turned remixes of Sade ballads into club classics, and a raft of hip-hop artists repeatedly sampled her.

So when the owners of East River Tattoo fired back on Instagram, posting a screen shot of the Yelp review beside a caption that said, “Proud to be shattering your expectations of what a tattoo shop should be, every day of the week,” obviously an army of Sade obsessives rushed to the store’s side.

“All that says is your understanding of the world and what’s happening in it… Is shall we say, limited lol,” one wrote.

Sade is one of the most relentlessly quiet famous people on the planet. But in her extended silences, her place in the pantheon of cultural influence has only grown more enormous.

This impact includes tattoos. More than 20 East River Tattoo clients have had their bodies adorned with Ms. Adu’s visage over the last year or so. A manager noted that that was 20 more requests than they’d gotten for Madonna and Janet Jackson.

The most famous Sade tattoo, however, belongs to Drake. He premiered it on Instagram this March. In it, Ms. Adu’s hair is hidden, Nina Simone-like, beneath a turban.

In February 2017, the street wear brand Supreme put Ms. Adu’s image on a coveted limited-edition T-shirt. In March, Reese Witherspoon’s Type A character on “Big Little Lies” established her remove from pop culture when she hears Sade on the car stereo and mistakes it for Adele.

Demand for T-shirts from Sade’s 1992 and 2001 tours has so outstripped supply that vintage sellers like Chico’s Closet in Los Angeles have largely abandoned eBay (and its commission fees) and moved to Instagram, where the mere act of hashtagging Sade leads to whack-a-mole-like sales.

Some of this Sade fever can be traced to Patrick Matamoros, 41, a high-end dealer who finds rare T-shirts, distresses them to perfection and then places them on to the backs of celebrity clients such as Rihanna, Diplo and Mark Ronson.

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Two years ago, Mr. Matamoros sold a tee from Sade’s 1993 Love Deluxe tour to Kanye West. “I’d sold Sade shirts to famous people before that, but something happens when Kanye wears a shirt that I still don’t understand,” Mr. Matamoros said on a recent afternoon.

This conversation was in his Lower East Side apartment, and he was in a Run-DMC shirt and a Sade crew hat that he sells for as much as $600.

He picked up a vintage Phil Spector shirt and poked a hole through one of the sleeves with his big toe.

“I used to say to people about Sade, ‘This isn’t going to impress everyone in the room,” Mr. Matamoros said. “Get an Iron Maiden shirt if that’s what you want. Sade was for two people in the room, but it was the right two people.”

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Not anymore. Now, everyone wants them and Mr. Matamoros says even he rarely gets them without paying at least $300 a pop, which happens to be more than any other female singer alive today.

Much of the current fascination with Sade derives from the fact that her fans know so little about her, starting with the pronunciation of her name. (Many Americans believe it’s pronounced Shar-day; it’s Sha-day.) In an era that rewards people less for their talent than for their associations with other famous people and the ability to leverage those associations over Instagram and Twitter, Sade’s disinterest in self-promotion has had a reverse effect.

Her longstanding lack of interest in speaking about herself makes the world more likely to want to speak about her.

For college, Ms. Adu went to what is now called Central Saint Martins, in London, then and now the world’s most prestigious fashion school. To make extra money, said Albert Watson, who photographed the covers of the band’s “Love Deluxe” and “Lover’s Rock” albums, Ms. Adu took a job selling clothes at the Camden Street Market.

She began singing backup in a local band, and moved to frontwoman only reluctantly. “The lead singer left,” she later said.

Sade models at a Spandau Ballet fashion shoot in New York City in 1981. Credit Ebet Roberts/Redferns

It turned out she was great, with a breathy voice that was heard by Stuart Matthewman and Paul Denman, playing in a band called Pride. They asked Ms. Adu to start singing with them.

In 1982 or 1983, Mr. Matthewman and Mr. Denman left Pride and formed a group around Sade.

They signed to Epic Records, where executives quickly realized they were dealing with an artist with no direct historical precedent.

“She was one of those rare artists I fell completely in love with because she came just the way she is now,” said Susan Blond, a former vice president and publicity director at Epic who now heads an agency where clients have included Aerosmith, Will.I.Am and Morrissey.

“She was very young, but she was very sophisticated,” Ms. Blond said. “She didn’t follow anyone else’s style. No one was as beautiful or had as sleek of a look as her. She didn’t mind designer clothes, but you’d never ever look at her and say, ‘Oh that’s a Chanel outfit.’ She never looked like a brand. And her songs seemed to become classics immediately.”

In a way, Ms. Adu’s sphinx-y stare, keen fashion sense and interest in Afro-Caribbean rhythms owed a debt to Grace Jones, but her pensive lyrics and languid delivery of them flipped the script by placing romance above sex.

When Ms. Adu sang about a male gigolo on her breakout hit, “Smooth Operator,” she was lamenting what happens when “sentiment is left to chance.”

The saxophone signaled sorrow. Ms. Adu wasn’t asking — as Ms. Jones did — for a guy to “drive it in between.”

Shortly before Sade won the 1986 Grammy for best new artist, she appeared on “Saturday Night Live” with Tom Hanks, who recalled the experience in an email: “It was the first time I did ‘SNL,’ which is a major event an anyone’s life, a heady week of being surrounded by all that history. I’d never been in 30 Rock, much less invited to work on the 17th floor or in Studio 8-H. I thought the big talisman for being on ‘SNL’ was the job of saying ‘Ladies and Gentlemen, Sade.’ which is actually written on a cue card, by the way.’

Calling her elusive or mysterious might color her as unkind or remote. She was not that. She was, rather, just very comfortable in her command of her art, as well as her presence. Having very little in common with her, save the close approximation of dressing quarters, a bit of me yearned to be as cool and composed as Sade. She remains a Smooth Operator, no?”

Dan Beck, a former senior vice president at Epic who worked on the United States promotion for Sade’s first four albums, said, “There was grace to everything she did.”

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Although Ms. Adu looked forward to the publicity campaigns of record releases about as much as one would a root canal, Mr. Beck said, this wasn’t because she was temperamental or diva-ish.

She merely regarded the project of explication with suspicion. She seemed to operate according to the principle that narcissism was not the precondition for artistic exploration, but was instead its enemy.

“She never enjoyed promotion of any type,” Mr. Beck said. “It was painful for her. Eventually, I flew over to London to see her and we struck a deal. I said that if she would commit to giving me three weeks of nonstop publicity for each album, everything but the kitchen sink, VH1 and radio stuff and photo shoots, I would go back to my counterparts at the label and get them to put everything they needed into that time period. I said, ‘You’ll hate it but we’ll get it all done and when you’re done you’re done.’ And she laughed, and that’s what we did for the next two albums after that.”

(She and her bandmates also hired the manager Roger Davies, who guided the second half of Tina Turner’s career and long understood that mystery equaled timelessness.)

As the years went by, the break between albums stretched ever longer. She wanted to have normal relationships. She wanted to record when she actually had something to say.

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Sade’s 1992 album, “Love Deluxe,” arrived four years after “Stronger Than Pride.” Ms. Adu smiled as she told Mr. Beck she might not have gone back into the studio to record — except the guys in the band wanted to return to work, he said. “I thought that was so sweet.” (In a 1992 interview she said, “It’s good that we stopped and didn’t try to make another one off the back of the previous album. You get some perspective on why you’re making a record.”)

Then, she did the photo shoot for the album and Mr. Watson, a contributor to Vogue who directed a number of Sade’s videos, proposed shooting her topless with metallic body paint, her hands covering her chest.

“She said, ‘I don’t mind. I’ll do that for you, but I don’t want it to be anywhere near the album cover,’” Mr. Watson said. “I said, ‘The shoot is for you. You control all the images.’ Then she looked at it and said it was too sexy.” Eventually, in conversation with the band, she agreed to use it, but the image remains an outlier in the way she has chosen to display herself.

A year later, Sade declined to release a house remix of “Pearls,” perhaps because there was something a little unseemly about people dancing to a song about the Somalian civil war. Then, a bootleg of it began making the rounds to D.J.s such as Junior Vasquez and Frankie Knuckles, who turned it into one of the era’s defining club tracks.

In 1995, a marriage to the Spanish film director Carlos Pliego ended. Ms. Adu later said the pair had a difficult time navigating the demands of global fame with their private relationship. For a time, she lived in Jamaica with Bob Morgan, and they had a child.

An eight-year stretch between albums yielded “Lover’s Rock,” which had lots about romance but also brought a quiet force to songs about issues facing black people. The video for “King of Sorrow” was a masterstroke of Sade-ness, where she wore ball gowns and a bandanna, scrubbing a child’s shoe clean. Was it a cautionary tale for single parenthood or a fashion spread devoted to it? Who could say. It was lovely.

By the mid-aughts, Ms. Adu had become involved with a former fireman named Ian Watts. With one child each, they had settled into a countryside cottage near Stroud, England.

All this time, in luxurious quiet, her legend grew. The parasitic music business had driven many black female singers to seclusion, before Sade. The difference was that Ms. Adu appeared not to be combusting but thriving.

Her fans yearned for more material, all the while respecting her resolute privacy.

One secret to her absence is that it is not so total as to be suspicious. Tours in 2001 and 2011 showed her to be in fine form. (And the time away only helped build interest. The first tour for her 2001 album, “Lover’s Rock,” grossed $26 million. The second, for “Soldier of Love,” grossed $50 million.)

In 2012 Mr. Watson had a retrospective in Hamburg, and Ms. Adu flew in without any pomp or circumstance. She simply treated it as if she was showing up for a friend and smiled luminously as she sat with him in her trademark earrings, silk shirt and jeans.

When the exhibition was too crowded to really view the work, she returned the following morning to see it again, Mr. Watson said.

Ms. Adu can also sometimes be spotted on her cat-loving child’s Instagram. On Mother’s Day this year, this undated portrait was published. Back in January, on the day she turned 58, a recent picture appeared. She looks impeccably happy.

Even with so little of her, you can see her look everywhere. Just last week, T:, The New York Times Style Magazine put Nicki Minaj on a cover, her hair in a black ponytail, a pair of gold hoops dangling.

Lauren Tabach-Bank, the magazine’s entertainment director, didn’t hesitate when asked whom they were channeling. “Sade,” she said. “You never know how someone’s going to react, but Sade is universally respected and lauded by musicians of all genres. Nicki saw the images and was like, ‘Sade, Oh my God. I love it.’ It felt expensive, cool and timeless.”

There’s talk of a Sade album coming next year, but even Mr. Watson, who sees her with some regularity, says he isn’t sure.

“It’s always like that with Sade,” he said. “Time will go by and she’ll start working on it. For her, it’s like getting out of bed on a Sunday morning. You know you don’t want to do it, but at some point you just do it.”

“When we were having our first success with her, I said, ‘This lady could have a hit album when she’s 90 years old.’ Most artists try too hard,” Mr. Beck said. “And consciously or unconsciously, I think people have a special appreciation for someone who isn’t out there waving their résumé at you every five minutes. She’s completely unique.”