Janet Jackson can still remember the first song she wrote.

She was nine years old and bored, one rainy afternoon in 1975.

Her older brothers – already international megastars – had just returned from an exhausting 10-month world tour. While they recuperated, there was no-one to keep her entertained.

Finding herself at a loose end, Janet sneaked into the recording studio in family's backyard in Encino, California, and started playing a tune she called Fantasy.

"I laid down the drum track, I did the background vocals, I sang and I played everything on it," she recalls.

With an empty day successfully filled, she left the tape on the system and went to bed, not thinking much about it.

But when she arrived home from school the following day, the song was blaring down the driveway.

"I was so embarrassed. The studio door was open and Mike was listening to it," she says, referring to her brother Michael.

"I think Randy was listening to it, my father was listening.

"Then my father said, 'You're gonna sing'.

"I said, 'No, no, no, I want to go to the college and study business law.'"

But when Joe Jackson told his children what to do, they fell in line.

"It was kind of hard [to argue] because, look at where he led my brothers," she says.

"So I said, 'OK, I'll give it a go.'"

Nearly 50 years later, Janet Jackson is one of the most successful recording artists of all time.

With era-defining albums like Control and Janet, she has sold more than 100 million records, been named an MTV Icon and, in 1990, broke the glass ceiling by becoming the first woman to be nominated for best producer at the Grammys.

"That was jaw-dropping for me," she says. "You think it should have happened a long time ago."

We meet backstage at the Barclays Center in Brooklyn, where the star is about to play the 73rd show of her Together Again tour, which reaches the UK in September.

Her most successful concert tour to date, it explores Janet's entire career, from the sweaty R&B grooves of Nasty and Rhythm Nation to seductive slow jams like That's The Way Love Goes and Any Time, Any Place - all performed with her trademark whip-crack choreography.

On stage, she's a commanding presence. In person, she's shy and softly-spoken.

"I don't like talking," she confides. "And I don't like interviews. I don't think I'm very good at them."

In the midst of a New York heatwave, this puts a chill up my spine. I've watched enough YouTube videos to know Janet can be awkward and distracted under the spotlight.

But the fears quickly melt away.

Today, Janet is candid, relaxed and funny - not only breaking into song, but busting out dance moves and, most surprisingly of all, joking about her ill-fated love life.

"How many times have I been married now?" she laughs. "Three, I think."

There's an ease that suggests the star has resolved – or at least found a way to make peace with – her battles with low self-esteem and body image.

The key, perhaps, is that she has someone else to care for.

Her first son, Eissa, was born in 2017 and is present for her New York show, standing proudly at the side of the stage wearing ear defenders.

"Being a mum is the most beautiful thing," she says.

"I love every single minute of it."

Eissa is now seven, the same age Janet was when she made her TV debut, appearing with her brother Randy in a comedy sketch on the Carol Burnett Show.

"I don't ever remember being asked," she says, a hint of sadness in her voice.

"I just remember doing it."

Before long, she was taking roles in the TV sitcoms like Good Times and Diff'rent Strokes.

In her teens, she released her first two albums, Janet Jackson and Dream Street. One contained a surprising duet with Cliff Richard. Both failed to sell.

Then, when she was 18, Janet suddenly and unexpectedly eloped with doe-eyed soul singer James DeBarge.

Their marriage was annulled after eight months, but not before it threatened to ruin her reputation.

At the time, DeBarge was a drug addict who would often disappear for hours at a time – including on their wedding night. Janet found herself scouring the streets for him at all hours of the night and day.

"I was doing the TV show Fame at the time and I'd be late for work and hold up shooting," she says, wincing at the memory.

"I wasn't being irresponsible. I just felt that [James] needed me more than the show.

"I got spoken to a few times by the producers. I’m not sure they were that fond of me."

Ferociously cool

Janet eventually asked to be released from the show, deciding to give music "one more chance".

Rejecting her father's preferred producers, she hired Minneapolis funk masters Jimmy Jam and Terry Lewis for her next album, Control.

Known for hits like The Time's Jungle Love and The SOS Band's Just Be Good To Me, they teased out a new sound for the singer – full of industrial-strength rhythms and strident, assertive lyrics.

The stories were drawn directly from Janet's life. What Have You Done For Me Lately was a sassy retort to DeBarge, while Nasty was written after Janet and her friend were harassed by a group of men on the streets of Minnesota.

The title track, meanwhile, was a defiant celebration of independence.

"When I was 17, I did what people told me / Did what my father said, and let my mother mould me / Now I know I've got to take control."

Jam and Lewis helped Janet express a side of her personality – self-confident and in command – that the public had never seen before.

And they did it by getting her drunk on ice cream.

"They did!" she laughs. "I didn't know the ice cream had real rum in it because I really didn't drink.

"But I wasn't like an idiot, tripping and stumbling over myself. I just felt a little woozy in the head and I was more forthcoming with my story."

"All of the songs we did with her on Control record had attitude," says Jimmy Jam.

"She always had a lot of attitude in the parts she played on TV and we just thought, that's not coming out in the music. So we tried to make really aggressive tracks, really hard-hitting tracks, because we knew she could pull them off."

Ferociously cool, Control became an MTV staple thanks to eye-catching videos like Nasty and The Pleasure Principle – all featuring Janet's punchy choreography.

Surprisingly, she never had formal training – learning her moves from classic MGM musicals. Her only experiences of dance classes ended in disaster.

"Mother tried, when I was very little, putting me in ballet," she says. "But I've got a booty. So she [the teacher] would say that I'm not tucking my butt in enough.

"Then she hit me.

"I was young. I was little. Maybe four, five. And so mother took me out."

A second attempt at taking classes in her teens also ended badly.

"I remember that [my teacher] got a little too close to me and I felt very, very uncomfortable. And I remember coming out of the class and telling my mother and she said, 'You're never going back'.

"So I never really studied."

Music industry pushback

Control was a monster, selling 10 million copies and spawning six hit singles.

For the follow-up, Janet's label asked her to make a concept album about her family.

She entertained the idea briefly (You Need Me, a song about her difficult relationship with Joe Jackson, eventually became a B-side) but eventually rejected it in favour of the socially-conscious lyrics of Rhythm Nation 1814.

It was inspired by the dawn of 24-hour news. Janet would have CNN running in the studio, and reports about homelessness, drug crime and school shootings made their way into the lyrics.

"I was seeing things that were bothersome to me and wanting to write about [them] in the hope I could make some sort of a difference."

Her goal, she says, was not to make political songs in the style of Tracy Chapman or U2, but to make sneak messages into music "that was really funky".

"People would get into the groove of it, then stop and listen to what the message is and say, 'OK, wait a minute, that's really interesting.'"

Is she discouraged that, 35 years later, we're still fighting the same problems?

"It's crazy, isn't it?" she sighs.

"Have we made some strides? Yeah, I think we definitely have. But there's still so much further to go."

Sexism is another topic Janet has addressed repeatedly, in songs like The Skin Game and New Agenda ("because of my gender, I've heard 'no' too many times").

Even after the success of Control, she clashed with men who wanted to dictate her career.

"In the industry, [I was] told no, more than once. 'You’re a girl. Girls don't do that.'

"And I was like, 'Well, why not? What's wrong with trying?'"

The obvious conclusion would be that Janet got pushback when she delivered the soft, sensual and explicit Janet album as the first record of a multi-million dollar deal with Virgin Records.

But she says the label "loved" the sound and feel of songs like That’s The Way Love Goes, If and Any Time, Any Place. The Janet album – promoted with a topless photoshoot for Rolling Stone – outsold even Control, shifting more than 14 million copies.

It was the 1997 follow-up, The Velvet Rope, that caused more consternation. Dark and disturbing, it amped up the sex while addressing topics like domestic violence, depression and same-sex relationships.

The album's lightest moment was Together Again – a bittersweet house anthem written after one of her friends died of Aids.

The lyrics aren't particularly specific: Janet’s promise to meet again in another life works for anyone who has lost a loved one. But the track made executives jumpy.

"I think it was because of the era of Aids and all that was surrounding it. But I had lost a lot of friends and a lot of people that I knew to it – and it was heavily on my mind.

"But I never really envisioned myself singing Together Again," she adds.

"Even though I wrote it for myself, I always thought it would be better with someone like [The Weather Girls'] Martha Wash, who had that kind of voice."

Together Again has become her signature song. It's her most streamed track on Spotify, as well as the title of her current tour.

The stage production may not be as expensive as her theatrical 1990s tours – with just five dancers and a minimal set - but that gives the show a more intimate feel.

Janet lets her guard down, turning her mic to the audience during Again, cheering for fans and blowing kisses as they sing along.

She also rewards them with a clutch of cherished deep cuts like Feedback, So Excited and All Nite (Don't Stop).

They're all late-period songs that would have received more love if the Super Bowl "wardrobe malfunction" controversy hadn't damaged her career (Janet's music was blacklisted by MTV and hundreds of US radio stations amidst the backlash).

One of the tour's most powerful moments comes when she performs Scream, duetting with video footage of Michael, who died in 2009.

It's still emotional "listening to him every night, seeing him, remembering us," she says.

"Mike and I wrote that song in New York, in his apartment," she reminisces.

"So [I relive] that whole journey, listening to him sing it [and remembering] what he was going through at that time.

"And just me being his little sister, always by his side, and being that support system. That's always been my role."

The concert wraps up with Together Again, during which Janet catches a bouquet of flowers and bounds across the stage with her dancers, beaming from ear to ear.

The audience in Brooklyn is studded with stars, including fashion designer Christian Siriano, soul singer Maxwell, drag queen Kevin Aviance and R&B star Tinashe – whose current single, Nasty, tips its hat to Janet's song of the same name.

"Everything about her is 10 out of 10. She's the blueprint," Tinashe says. "A huge reference point for me. She’s such a queen."

After the show, Janet meets fans backstage, her hand pressed to the small of her back after pulling a muscle dancing to What Have You Done For Me Lately.

Nonetheless, she's in good spirits – looking forward to a "mummy day" between shows, and asking whether the setlist should change when she comes to Europe.

Flustered, I deflect the question by asking whether putting together the career-spanning concert has given her new perspectives on her life.

"I'm just thankful that people are still interested in seeing me do this," she replies.

"I feel very blessed."

The UK leg of Janet Jackson's Together Again tour starts in Birmingham on 27 September, with further dates in London, Manchester and Glasgow.