Behind the music: the secrets of Sade's success

She's sold 50m records worldwide – almost half of them in the US – and has had a career spanning four decades, all of it on her own terms, while barely compromising her sound. Throughout, she's kept herself out of the limelight, avoiding the usual press junkets associated with releasing a new album. So what's the secret behind Sade's continuing success?

When Robin Millar, who produced the band's first two albums, first met them in 1983 they'd never been in a proper studio. The 24-year-old Sade Adu had just finished studying fashion design, while working on her creative writing skills. They had some rough, homemade four-track demos of Your Love Is King and Smooth Operator that sounded like a funk band playing free jazz. "It was basic, but the songs were good – and then there was that voice," Millar says. "I've always thought there are certain voices that make people feel better: Bing Crosby, Frank Sinatra, Nat King Cole and Ella Fitzgerald. And when I first heard Sade I really felt she had it ... She also had an amazing effect on people in the studio, both men and women – her charisma and how she looked."

He booked them in for a week. The limitations of not having computers had an impact on the sound. "We used a real piano and a Fender Rhodes piano, painstakingly synching them up," Millar recalls. "Of course, three years later you could do this easily, using midi. But it probably wouldn't have sounded the same. To do this we had to formalise the parts, getting away from the free-jazz thing."

The band's manager took the demos around to record companies – and every label turned them down. "They said the tracks were too long and too jazzy," says Millar. "They said: 'Don't you know what's happening? Everything is electronic drums now: Tears for Fears, Depeche Mode.' This was a bit of a blow, because when we played them to people who came by the studio we'd get a fantastic reaction."

What they needed was some DIY thinking. Sade's boyfriend played the tracks to friends who worked at style-bible the Face. They liked both Sade and the music and put her on the cover with the headline: "Sade, the Face of 1984." The band quickly organised a gig at the club Heaven, inviting journalists who witnessed 1,000 people being turned away at the door. The next day all the record companies tried to sign them. Most of the labels wanted to send her to the US to work with big producers such as Quincy Jones. But Sade had a clear vision of what she wanted to do – so instead of the biggest offer, she took the deal that allowed her to finish what she started. "The versions of Your Love Is King and Smooth Operator on Diamond Life are exactly the way they were at the end of that first week," Millar says. "We never remixed them or remastered them. They're the same versions that were rejected by everybody."

They recorded 15 tracks in six weeks. Then Sade insisted on cutting the album down to the nine tracks in which she most she believed. The label wanted to send a few tracks to the US for some "cool" mixes but Sade refused, saying the album was exactly how she wanted it. It was quite a battle, which she won. (Hearing remixes by Jay-Z and the Neptunes on her newly released greatest hits album, part of me wishes she'd continued to resist tampering with her music.)

It was clear Sade was good at realising the bigger picture, right from the start. While recording, she worked with the label's PR and marketing departments, using her background in fashion and creative writing to crop pictures and look at copy – not allowing a sentence, snapshot or picture to go out unless it fitted. Once the album was released it was apparent that the label had been right in allowing Sade to hold the reins. Diamond Life went top 10 all over Europe and sold more than 10m copies worldwide. "It turned out there were an awful lot of people who didn't want to buy another Tears for Fears and Talk Talk album," Millar says. And Sade sounded like nothing else.

They went on to court the American R&B audience with Hang on to Your Love, which went to No 1 in the R&B charts, followed by Smooth Operator, which broke her in the US. The album ended up selling almost 4m copies in the US with the follow-up, Promise, selling 4.5m (9.3m worldwide) – the first British black artist to hit that big in America.

These numbers are almost unheard of today. But Sade's success has continued through the decades, despite letting up to seven years lapse between releases. Millar attributes some of this success to the fact Sade makes records you can play all the way through. "I think that's one of the reasons they haven't dated, going back to the first album when she threw out the uptempo tracks, because they didn't fit in." There is, of course, also the sexiness of the music – and the fact that having never followed trends gives the music a timelessness. A Sade album is instantly identifiable.

Sade is still more comfortable in the studio than on stage, Millar says. "It's to do with style. You can craft something to perfection and you can crop pictures, but when you walk on stage you're going to look how you look and sound how you sound." She told him the reason she didn't move on stage for the first few years – which everyone considered cool – was because she felt rooted to the spot. "I feel like even if I just shuffle my feet I'll look ridiculous," she explained. A tour manager I spoke to said she looked absolutely petrified before going on stage at Live Aid.

Millar is grateful that Auto-Tune didn't exist then.. "One of the things that makes a string section sound great is that they're all playing with a slightly different sound, pitch and timing. If you tune them all up they sound smaller and thinner. Where it [Auto-Tune] sounds most inappropriate is with someone such as Michael Bublé. Sinatra used to sing slightly flat all the time, and so did Sade – that's what gave her that melancholic sound.

"Mind you," he concludes, "it doesn't seem to affect sales."