Chaka Khan has a question. “What’s that TV show, where it’s just families sitting down and looking at the TV? Chat Box?” Gogglebox? She claps her hands delightedly. “Gogglebox – oh, I love that! And that quiz programme where the enforcer comes on and it’s like a big black guy, or a big woman.”

Erm, The Chase? With Bradley Walsh? She nods. “So good. I like funny shit.”

It goes without saying that I didn’t expect to end up discussing Bradley Walsh when I arrived to interview Khan, a woman who could call herself the Queen of Funk without much fear of starting an argument. A minute ago, we were talking about her vast influence over modern music, something that is evident from her new album, Hello Happiness, a collaboration with the producers Sarah Ruba and Switch, the latter best known for his work with MIA and Major Lazer. It is audibly the work of people who, as Khan puts it, “made it abundantly clear that they didn’t have to Google me”. Its sound is based on an intricate knowledge of her back catalogue – the vivid funk she recorded with Rufus 40 years ago, the effervescent disco of her early solo albums, the electronic dance-pop of her biggest hits – and given a subtle 21st-century makeover.

Khan was telling me that she was less aware of her influence than she might be, because she doesn’t really listen to music at home, preferring to relax in front of the telly. And now here we are, talking about Gogglebox and The Chase.

It is certainly an unexpected turn of events, but nothing about Khan’s life or career seems straightforward. She was born Yvette Stevens 65 years ago in Hyde Park, a progressive, bohemian, racially mixed “island amid the madness” of 50s and 60s Chicago: “A great city, very rich in terms of the arts, but it’s so racist it’s hard get to the friggin’ arts if you’re black. You have to grow up in a specialised community, which mine was.” Her mother was a strict Catholic, but her father was a beatnik: “My sister and I used to go on his nocturnal excursions by the lake in the park. The weed was thick in the air, the wine bottles were flowing, music was playing – as tight as it was, I had a pretty magical life.”

Her father remarried, to a civil rights activist who encouraged Khan to speak at rallies; by the age of 14, she had been recruited by the Black Panthers. “I was a kid, so they really just had me selling the Panther paper on the corner, barefoot in jeans. I was totally against all the sock hops and shit my school had to offer to keep the natives quiet. We used to call them ‘slave gatherings’. So, I had my combat boots on, my green khaki pants. I didn’t feel in danger – it wasn’t like that. We were doing the right thing. However, when a gun came into my hands, a .38 that I hid in my room … I’m telling you, every moment I had that gun it changed me. I felt physically sick. I threw it away into Botany’s Pond by Chicago University, then I felt better. That finished me with the Panthers.”

Khan in 1975: ‘The thing was to have a white band with a black chick out front.’ Photograph: Len DeLessio/Corbis via Getty Images

Instead, she concentrated on her musical career, singing jingles, performing with a succession of bands in the clubs around Chicago’s Rush Street before landing a gig with a racially mixed funk band called Rufus. “The thing back then was to have a white band with a black chick out front – that was major money, made the club owners interested.” She laughs mordantly. “Another racist phase that passed through Chicago.”

With Khan on vocals, Rufus were an immediate sensation: she had both a hell of a voice and a precocious, raw stage presence. She was 17 years old when they were offered her a record deal, still legally a child. When her mother refused to sign the contract on her behalf, she got married to her boyfriend, lying to her parents that she was pregnant. By the time of their first hit, 1974’s Stevie Wonder-penned Tell Me Something Good, she actually was. “Yeah, everything happened to me like that: bam. And, yeah, it left some scars, created some bad habits. Why wouldn’t it?”

Despite their success – six gold or platinum albums in five years, 25 hit singles on the US R&B chart – Rufus were a highly combustible band. There were endless line-up changes. There were fistfights in the studio, issues with managers. “I had nothing but rip-off artists, until just lately,” she sighs. The atmosphere wasn’t much helped when the record label started billing the band as Rufus featuring Chaka Khan, or by tension between the band members and Khan’s second husband, Richard Holland. “They didn’t want me to have a husband,” she shrugs. “When the band first went on tour, every night, after a gig, they would all do a walk-through of my room to make sure I was by myself. They didn’t care who it was – no one could come and visit me. They were just very possessive of their little diamond.”

Eventually, Khan struck out on her own, scoring an immediate hit with the Ashford & Simpson-penned I’m Every Woman. She kept making albums with Rufus out of “guilt”, although the results were often spectacular, not least 1979’s superlative Masterjam; ironically, their biggest hit together – 1983’s Ain’t Nobody – came after Khan had left for good. Her solo career was soaring. With the producer Arif Mardin, she made a succession of wonderful albums, on which, as she characteristically puts it, “every song’s a motherfucker”. She was prodigiously, intuitively talented – unable to read music, she would nevertheless arrange her own songs, singing the notes she wanted to the horn and string sections – and remarkably adaptable, throwing out albums of jazz standards alongside collaborations with Rick James. Just as Rufus had transitioned seamlessly from funk to disco, so Khan survived the disco backlash with barely a scratch.

Khan in 1975, when her band Rufus were riding high in the US charts. Photograph: Anwar Hussein/Getty Images

But behind the scenes, Khan’s life was going haywire. She ended up locked in battles with her record label. “Assholes,” she says, flatly. “They didn’t know how to work me, what category to put me in. Hell, they didn’t have a clue. I get it – no category. That means do everything – let’s do it all! But, see, that’s too much work for them. I went in one time, they’d hired another A&R, who told me: ‘We need you to sound like Mary J Blige.’ I said: ‘You motherfuckers need to get Mary J Blige then, and leave me alone.’ That’s when I really decided, ‘I’m done.’”

She struggled with addiction – to cocaine, heroin and alcohol – for most of her adult life. Remarkably, it did not seem to interfere with her career: by her own admission, she was “getting fucked up” throughout her commercial peak. “Very good at compartmentalising,” she nods. “All through the 80s, I knew when to abstain, I really did. I had lines of demarcation in my life, and I practised them. And, also, I was very aware of my health; that was important to me. When I was with the Panthers, my girlfriends and I were all into breaking our own bread, taking our herbs, fasting one week out of every month. So there were certain other habits I got that I never did stop. It was the healthy living that brought me through drugs alive, I’m sure of it. I would get massively fucked-up for a couple of weeks and then I’d take, like, a herbal shut-down where I’d stop and just go on plants. So that helped me a lot.”

It was the healthy living that brought me through drugs alive, I’m sure of it Chaka Khan

She says her last bout in rehab – for an addiction to opiate painkillers prescribed after a knee replacement operation – was provoked by the death of Prince in 2016. They were close friends – he wrote her 1984 UK No 1 I Feel For You, and they regularly collaborated. She signed to his NPG label in the late 90s, resulting in the brilliant overlooked album Come 2 My House – although her interactions with him seem to have been as bizarre as everyone else’s. They met when he rang her hotel room in San Francisco, pretending, for reasons best known to himself, to be Sly Stone. “I could have sworn it was Sly; Sly and I were very close. He said: ‘I’m at a studio in Marin County doing this album, do you want to come?’ So I drove for 100 years and get in there and it’s like dark and sterile and very eerie. There’s this little guy with a guitar. I said: ‘Excuse me, where’s Sly?’ and he put his guitar down and said: ‘I’m sorry, that was me.’ ‘Well, who the fuck are you?’ I was truly pissed about this. He told me who he was, I said: ‘OK, nice meeting you, but I’m really pissed now, so goodbye’, and I left.”

She says she had no idea of the extent of the Prince’s own issues with painkillers. “I never, ever got any indication that he was on pills. I knew he was doing certain things, I knew he had a couple of bouts with acid and all that. That’s OK. A one-off here and there, you got the money, you ain’t working. You like acid – go do it. But he was totally against drinking; he’d drink red wine occasionally, not a lot. He starved himself – he wouldn’t eat unless it was this or that; he was very particular. What comes to mind is someone who was very health conscious as opposed to …” Her voice trails off and she shakes her head. “Secrets kill. Secrets kill, and if he hid from me for so many years where he was really at, and I was like his confidante in many ways, you know … It’s hard to keep a secret like that from me. So I learned a lot, you know. I just said: ‘I better go check myself.’ And I’m alive maybe because he’s dead. I went to a doctor and I said, ‘Here’s the deal’, and he told me there are certain pains you’ve just got to live with, that’s part of life.”

Khan performing in Toronto, Canada, in September 2018. Photograph: Rich Fury/Getty Images for Netflix

These days, she is a teetotal vegan, her only vice the packet of cigarettes on the table in front of her. In recent years she has spent much of her time raising her granddaughter – she won permanent custody after reporting her son and his partner as incapable due to drug addiction – whom she describes as “my best investment”, and whose own lack of musical ambition seems to delight her. “I love it – she’s not interested in my fucking shit. I can’t get her to come to a concert and see me sing all about her – she wouldn’t give a damn. She doesn’t care. She wants to be a doctor. She’s so in the right place.”

And so, Khan says, is she; despite the turbulence of her past, “at 65, I’m still looking forward to shit”, she laughs. Hello Happiness “has put a new spark in my career”. There’s a forthcoming collection of Joni Mitchell covers to think about, as well as her charitable foundation, which works with autistic children and is currently engaged in trying to re-establish the after-school music programme in Minnesota “that Prince went to when he was a kid, where he got a chance to play with older cats all the time. We’re just trying to play forward Prince’s dream – the shit that saved him may save others.”

And she is currently engaged in a battle with the aforementioned assholes at her old label over the rights to her back catalogue. “After 30 years, your shit should automatically return to you, but they’re trying to fight me on that. But not to worry, darling. I’ll be all right. I will be. I’ll be fine.” She lets out a throaty laugh. “You know,” she says, “I’m kind of an alpha chick.”

• Hello Happiness is released on 15 February