Sia thought she would retire and become a songwriter. Turned out her pop craft made her a bigger star than ever. In a rare interview, Sia talks writing, her demons and the power of saying "no"

Three years ago, Sia Furler tried to pull off a disappearing act that hasn't worked out so well. Burned out from a solo career that began in 1997, Sia wanted to stop recording under her own name and simply write for others. The hits came quickly, some featuring her vocals, and her fame grew instead of shrank.

Read Sia's Anti-Fame Manifesto

During that time, she's refused all interview requests, not wanting to be drawn into the celebrity culture that's hungry for details about the pop stars for whom she writes. But when she does agree to an interview with Billboard about her songwriting, she doesn't shy away from talking about herself or her desire to step away from fame: Within four minutes of sitting down, she explains her addiction to painkillers, alcoholism, medical misdiagnosis and the clauses in her contract with RCA for her next album that stipulate she doesn't have to tour or do press to promote it.

Sia is amazed at how things have worked out. "It shows the power of saying 'no,'" she says. New management; co-writes for Rihanna, Katy Perry and David Guetta; guest vocals with Guetta and Flo Rida; and appearances on the Great Gatsby and The Hunger Games: Catching Fire soundtracks have only elevated Sia's profile despite her protestation, "I'm retired."

"I get to sit at home with the dogs on the sofa, record in a closet in the office, send them off and, if I'm lucky, make a million dollars," she says.

She laughs, joyfully squirming on one of two couches in her living room covered by multicolored quilts. A broad smile appears as she talks about how her income from copyrights has "made things easier," paving the way for her to purchase more property and finance travel and parties for friends, not to mention do a good deed or two.

Her home of three years in the hilly Echo Park section of Los Angeles is also her workspace, with a small office for writing and an adjoining closet as a vocal booth. Here Sia has been working on her own album, with a hoped spring 2014 release. RCA CEO Peter Edge—a Sia fan for more than 10 years—says he needed nothing more than "blind faith" to sign her. The RCA team met with her in Los Angeles at the end of last year at her house, with the dogs running around, to hear her music.

"Soon as we were in the house I knew we weren't dealing with a regular artist. Working with Jonathan Daniel [of Crush Management] we crafted a deal uniquely for her," he says.

Billboard heard seven songs, most co-written with producer Greg Kurstin (P!nk, Kelly Clarkson). Tracks like "Fire Meet Gasoline" showcase the Sia who has lately been filling the song pipeline for Rihanna and Beyoncé. Others, like "Cellophane" and "Eye of the Needle," demonstrate her willingness to marry pop melodicism with emotional turmoil.

"I hear real lyrical depth in the stuff she is choosing to do herself," Edge says. "She has an unusual ability to express herself musically, rhythmically and in her breathing. I have heard plenty of singers say they like [a Sia-written] song, but they can't sing it the way she does. On the album, she's able to do songs that others couldn't sing the way she does."

Sia explains she writes her own material with Kurstin or other collaborators. "I'll sing where I want the note to go and they'll go around several chords until I say, 'That one.'

"The pop stuff I write to track. People send me the tracks—I probably get 10 a day—so I have to chose out of thousands. I feel the reason I'm getting the singles is that I'm good at picking the tracks, more than my having special skills."

She does, however, have a series of guidelines for her pop songwriting:

"The songs that work best are broad lyrically and have one strong concept in the metaphor.

"You have to sing [the metaphor] a lot of times in a lot of different ways.

"People like victory, victim to victory, and party time.

"Songs that have a negative chorus and sad songs without an uplifting chorus are harder to place.

"I have to keep it a lot simpler," she says, contrasting the pop work with songs she considers for herself.

Simplicity, though, doesn't translate into being less revealing. Ten years ago, the stories behind her lyrics were "all mine but I wouldn't admit to it then," she says. "I was too fearful, scared that I would be judged or somehow unlovable if people saw who I truly was. After 14 years of songwriting, I feel less vulnerable about telling the truth about what's really mine."

Read Sia's Anti-Fame Manifesto

That truth has changed through time. Three years ago, when she pulled back from her own career, she needed to regroup. "All I wanted to do was write for pop stars. For one reason or another it never happened for me. Then I got seriously addicted to Vicodin and Oxycodone, and I was always a drinker but I didn't know I was an alcoholic. I was really unhappy being an artist and I was getting sicker and sicker."

Things improved after a misdiagnosis was corrected and Sia was treated for hyperthyroid disease. Her medication was switched and she rested. The pills and booze stopped, and she began doing exactly what she'd always wanted.

The first project that Crush's Daniel brought was 10 tracks from Guetta. She chose "Titanium," writing the lyric in 40 minutes. Released in December 2011, it climbed to No. 7 on the Billboard Hot 100 and has sold 3.6 million copies, according to Nielsen SoundScan. For a follow-up, she wrote "Wild Ones" for Flo Rida in 15 minutes, she says. It peaked at No. 5 on the Hot 100 and has sold 3.8 million.

In both cases, Sia recorded vocal demos that wound up being used on the singles. What Daniel had pitched as a good way for her to get into pop songwriting, she says, was backfiring and keeping her name alive as a recording artist.

"They asked me to record ["Wild Ones"] over and over for almost six months. Eventually I said, 'OK, but don't put my name on it.' I was angry because we had already had this discussion. Jonathan said to me, 'I don't think I really believed you that you didn't want to be credited or get the recognition you deserve.'"

Obviously there weren't any surprises when her tracks were sent in for consideration for the films "The Great Gatsby" and "The Hunger Games: Catching Fire." Once she knew she would be the artist recording "Elastic Heart" for the latter's soundtrack, Sia says she felt there was a shift in the direction her RCA album could take. She's not planning to target the pop charts—she's created an animation project, Greta Gorgeous, and her band Surprise Party with that in mind. Her goal is something more stylistically and lyrically fearless.

"I don't care about commercial success," she says. "I get to do what I love and communicate whatever I want."

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