Sia's forthcoming album This Is Acting is comprised of songs she wrote for big-name artists that were subsequently rejected. But Sia insists these tracks have the potential to be huge hits, so she threw them onto an album to see if she's right.

Sia spoke candidly with Rolling Stone about her songwriting process, what it's like to write with artists she gels with creatively (Adele), artists she doesn't (Katy Perry) and artists who never show up (Kanye West).

Sia doesn't think she's a great songwriter so much as a prolific one.

"I think the reason I'm pretty successful is actually because I'm really productive, not necessarily that I'm a great songwriter. I think I'm a good curator, so I know how to choose tracks that feel like they're anthemic, or that seem to have an uplifting quality in the chorus. It really seems like the general public responds well to songs about salvation or overcoming something, or that everything’s going to be OK, or that things are fun. So yeah, I think that my skill is more upbeat curating, as in choosing the right tracks and then sort of trying to understand the will or nature of popular culture."

Sia feels like she's been pitching songs to Rihanna for years now.

"Mostly we've been pitching on Rihanna for the last couple years because she's been looking for a couple years. Well, it feels like a couple years. It might be one year. They're always looking for that first single.”

But Rihanna and Kanye West almost never show up to songwriting sessions.

"They'll entice me into a session by saying, 'Rihanna will definitely be there' or 'Kanye will definitely be there,' but it's hilarious because I turn up and, almost always, they never come. So I went into the studio to write for Rihanna with Kanye and neither of them showed up and stayed for less than an hour. They had two tracks. They told me what they had wanted. There were notes from Kanye, and I can't even remember what they were.”

Sia loved working with Adele, but apologized to her the next day for being “overly dominant.”

"I remember the day after I wrote with Adele. I wrote her saying, 'I'm just writing because I want to make sure I wasn't too overly dominant. I'm feeling a bit insecure that it was a bit annoying working with me as opposed to satisfying.' That was what my experience was like. I felt kind of insecure. I'm a fan and I want to do a good job and I want to work for the artist when I'm writing with them. Sometimes that can bring up insecurities. Then she wrote me back and was like, "What are you talking about?" [Laughs] I was like 'Riiight, OK!'"

Sia likes Katy Perry as a person, but she doesn’t like her approach to songwriting.

“[Like Adele, Katy Perry is] also quite dominant, and she's extremely analytical. I actually quit within the first hour of our first session. I was like, 'Can we both agree this doesn't work? Like our whole songwriting dynamic?' And she was like, 'I love it. It's like a puzzle to me. It's like a crossword.' And I was like, 'But this is boring for me. The analysis is totally boring for me. It feels like the enemy of creativity.' It was so cool to be able to have that conversation on why we wrote in such entirely different ways. I'm glad I didn't give up on it because I actually did get a song out of it, and we also really had a laugh because we were able to be authentic.”

Beyonce takes a very hands-on approach when collaborating with her camp of songwriters.

"The process is like a writing camp, essentially. She flies us all in and puts us all up. We all live in a house together — like five producers and five topline writers. She visits each room and will contribute and let us know what she's feeling and what she's not feeling. Lyrically, melodically, anything. She's very Frankenstein when she comes to songs. She'll say, 'I like the verse from that. I like the pre-chorus from that. Can you try mixing it with that?’”

Read the full interview over at Rolling Stone.

See Photos of Sia's Face