Hit maker: Sia Furler's midas touch has made her one of the hottest songwriters on the planet. Credit:Scott Gries/Getty Images The popularity of Sia’s songs in the last three years is extraordinary: Wild Ones (sung by Flo Rida, but with Sia’s backing vocals anchoring the song), Titanium and She-Wolf (both sung for DJ David Guetta) all made the top 10 worldwide. Diamonds (sung by Rihanna) topped the charts everywhere. Chandelier, the emotive lead single from Sia’s new album 1000 Forms of Fear has cracked the top 10 around the world, topped Australia's iTunes chart and is rising fast in the US. Those songs have been viewed over a billion times on YouTube, and that's not counting the songs she wrote for Katy Perry, Celine Dion, Christina Aguilera, Britney Spears, Ke$ha, Rita Ora, Jessie J and Minogue. Why is Sia so hot? “Because we’re all looking for the hit,” Minogue says. “That’s it. And she delivers.” Minogue says working with Sia was “nothing short of amazing ... she’s the genuine article,” adding that the pair share "a growing friendship".

Sheet musician: Sia Furler is shying away from publicity. The only thing Minogue sees stopping Sia is “if she chooses to opt out. As we get to know her character and how she does things differently, she may very well choose to do that, who knows. I hope not for our sake.” Kylie’s praise isn't unique. None less than Beyonce called Sia “a genius” after recording her song Pretty Hurts for the record-breaking album Beyonce. Russell believes the world’s best singers want to work with Sia because they are fans of her voice as well as her songs: "Sia has a really good way of making you feel her songs." He's not kidding: her 2004 song Breathe Me won cult status after closing the last-ever episode of hit HBO series Six Feet Under in 2005. It has since been covered by artists from Sarah Brightman to Kelly Clarkson.

Because we're all looking for the hit. That's it. And she delivers. When actress Lea Michele decided to eulogise her beau, Glee star Cory Monteith, who died from a heroin overdose last year, in song she chose Sia to co-write If You Say So. Russell says Sia's songs "have an element of revelation in them, revealing something about yourself, or realising something about yourself. “Sia right now, I think she’s hitting the nail on the head. It's kismet, isn't it? The stars are aligning. "The Pet Shop Boys said every artist has an imperial period, where they are defining the sound of pop and perhaps this is her imperial period.”

"Imperial" is a fitting word, not only because it describes Sia's growing influence, but also because, like a true empress, Sia gets her way. In the Stern interview, she revealed that while she mostly doesn't care what singers do with the melodies she gives them, most "stick with the program". And when they don't, and it matters to Sia, the recordings end up sounding how she wants. "Sometimes someone will change one note and that bothers me. One note. And I have to say, 'Can you go in and ... change it to the note it's supposed to be ... or go back and re-sing it with that note 'cause it just took away all the emotion'." An empress also issues edicts that, no matter how strange, pass into law. For instance, for this story Sia refused to provide any photos of her face and instead supplied shots of herself draped in sheets and garbage bags. But that was nothing compared to the promotional campaign for Chandelier which was rolled out with performances in which Sia’s platinum blonde bobbed hairstyle became a visual motif, while her face was hidden. In the song's official clip, tiny American tween dancer Maddie Zeigler manically dances around a dingy apartment in a flesh-coloured leotard wearing a Sia wig. Two weeks after it was released, Sia performed Chandelier on Ellen, sort of. She sang to the wall, her back to the camera, while Zeigler again leapt about. It was compelling but strange and somehow disturbing.

Then Girls creator Lena Dunham injected some undergraduate levity into the campaign by satirising Zeigler’s urban nymph; she pranced about on the set for Late Night with Seth Meyers in a white suit, again in a platinum wig, while Sia this time lay face down on top of a bunk bed. So far, so weird. Closer to home, the wig got yet another workout when Sia convinced David Russell to wig up and mime the audio for her acceptance speech after winning her second consecutive APRA Songwriter of the Year award on June 23. Russell believes that while the public expects a pop star to "lay themselves bare", some stars court it and others don't. Madonna, for instance, courts it. "[Sia] does not actively court that, she does not want that." "[Sia] uses the example of having had a conversation with a very close friend about having a cancer diagnosis and someone comes to ask for an autograph in the middle of it. You know that’s a horribly intrusive situation to be in."

One of the most interesting things about Sia right now, Russell believes, is that other pop stars are watching to see if she can break through to achieve major success while keeping back so much of herself. "A lot of pop stars who see the criticism [of their] public selves, the relentless online bullying ... are watching thinking, 'I'm gonna put the brakes on too and make this less about me as a person and more abou the art that I’m making'." In truth, the biggest-selling pop stars have been withdrawing from media that scrutinise them for years. Stars such as Justin Bieber, Rihanna, Pink and Beyonce all prefer to engage with fans via social media and rarely give interviews. When they do, it's either with friendly media who are unlikely to challenge them or outlets are ordered to not discuss the subject's private life under threats of the interview being cancelled or even terminated mid-conversation. Fairfax has challenged such provisions with Eminem and John Mayer in the past six months and had interviews withdrawn. Sia's approach is compelling and could even foreshadow the holy grail for stars – whose implied contract with the public has long been to sell a persona in return for the wealth that comes with mass popularity – but there's something unsettling about it. At the very least, using a fear of fame as the reason for hiding one’s face in performances to promote your product to more than 60 million people is a hefty contradiction. At worst, it could also be argued that it amounts to using real mental health concerns as part of a kooky marketing gimmick which, if nothing else, guarantees Sia will become more famous not less.

In her Stern interview, Sia suggested her promotion of Chandelier and 1000 Forms of Fear were as much about personal amusement as anything else. “All I really want to do is things I haven’t done, I’m gonna put a paper bag on my head and be on the cover of Billboard, see what I can get away with – if they’ll let me. And they let me. And I am literally giggling inside for like a month that I got away with it. “Doing the Ellen thing to the audience – getting away with it. Doing this weird Lena Dunham vibe, getting away with that, it just feels hilarious to me.” Russell understands why people might write off Sia's "fear of fame" argument as an ironic device to attract more attention: "That’s where we are in the world right now, everything is taken with a grain of salt ... everything is treated with the ultimate scepticism. "[But] a gimmick is something that requires a lot of behind-the-scenes conversations about "how do we make this a cool thing?". This is not that kind of thing, it’s not a gimmick.

"At the heart of this is the truth that she doesn’t want to be famous because fame is not what feeds her and that is the truth that is not going to change." Surprisingly for many listeners, in the Howard Stern interview, Sia seemed a million miles from the apparently hyper-shy, ultra-reluctant star the Chandelier campaign suggests. She quickly disarmed the often dominating Stern, freely opening up about her struggles with drugs and alcohol, a father who had two personalities. She calls Stern "babes" like he's her surfy boyfriend and seals his affections by singing Diamonds with an emotional depth easily outstripping Rihanna. Over 60 minutes, in a marathon public interview, Sia is consistently charming, funny and self-deprecating. Stern, a noted interviewer, presses Sia after she admits wanting a No.1 single. "I think touring is still an important part [of the music industry] and you want a No.1 single," Stern says. "You need to tour."

"I disagree," Sia says firmly. "[Appearing in public] disturbs my serenity." But as anyone who has struggled with mental health issues knows – and according to Sane Australia half the population will during the course of their lives – outward appearances can deceive. "To be honest, the hardest part of dealing with fame is not when you’re out doing it, it’s when you get home," Minogue says. "Who knows how [Sia] dealt with it at home? It’s like public speaking; you have to go and make a speech, you are terrified but you get through it. "It’s when you are home and you are dealing with yourself that the truth will come to the surface."

Many will wonder, if Sia is at such risk from public attention, why she continues performing in the genre of music that by definition attracts the most scrutiny: pop, which after all is short for popular. Sia has said she now owns four houses and is doing well enough from songwriting that she doesn't care if her album sells. In the circumstances, wouldn’t most people avoid the triggers for their anxieties? There's a good reason why Sia remains a pop singer and will likely make more solo albums. "[Sia wants] all the joy, all the accolades of doing what she was obviously put on the Earth to do," Kylie says. And like an empress, Sia is turning her fear into an advantage. "She sure is," says Kylie warmly. "It’s such a fine line. I don’t think just anyone [could succeed that way]. Is it the power of her songs? Is it how she manages to kind of obscure herself whilst [putting herself out there] in a really cool way? She's not just [saying] ‘I’m going to hide in my bedroom’. She’s out there ... performing on TV shows, but she’s doing it in her own way.

"She’s kooky, so we believe what she is doing now. It’s as direct as me showing my face on something or doing a photo shoot where there is nowhere to hide. That’s my truth in my connection with the audience and her truth is doing it her way, so even though she’s hiding, it resonates." Sia’s 1000 Forms of Fear is out now. Lifeline 13 11 14; Mensline 1300 789 978; Kids Helpline 1800 551 800 Sia's greatest hits If You Say So (Lea Michele)

The ballad Michele released to eulogise Corey Monteith after he died from a heroin overdose last year. Cynics will find this melodramatic, but they can go jump – it’s a remarkable piece of empathetic songwriting. Not released as a single. Titanium (David Guetta) The worldwide club smash hit opened doors for Sia in 2011. She wrote it but did not expect to be on the record. Remarkably, Guetta removed Mary J. Blige’s vocals because he preferred Sia’s demo.

Pretty Hurts (Beyonce) Beyonce called Sia “a genius” because of this critique on the pressure to be beautiful, which provided the soul to Bey's record-breaking self-titled album last December. One of the few Sia songs where the artist interpreted the vocal differently from Sia’s demo. Wild Ones (Flo Rida) Flo Rida’s name made this a party standard in 2012 and a No.1 smash, but it’s a great example of how Sia’s towering vocals anchor her songs. She has admitted embarrassment at the line “I want to shut down the club with you.”