David Guetta had to convince Sia not to retire from singing so she could record 'Titanium'.
Australian singer Sia was ready to give up recording new songs, but the super-producer - who has been behind hits for Black Eyed Peas, Jessie J and Nicki Minaj - only wanted her to appear on it when he heard the way she sung it to him.
He told Rolling Stone magazine: "When we recorded 'Titanium' she was like, 'Well David, I don't want to be an artist anymore. I'm done with this life. I just want to be a songwriter. I don't want to tour. I don't want to do anything like this anymore.'
"When I heard her voice on the track, I was like, 'That is insane. No one is going to be able to do better than this.' So she was like, 'OK. Last one!'"
The track has been a huge worldwide success, and meant David has managed to persuade Sia to appear on even more songs, including the chorus of Flo Rida's hit 'Wild Ones'.
He added: "She brought something really special. And we've kept working together on 'Wild Ones' and other records that are coming up.
"She's really amazing, and I'm glad she didn't totally stop."
David's latest album, 'Nothing but the Beat' is out now.