Christina Aguilera refused to show off her multi-octave singing range while working with M.I.A. - insisting she was "bored" of her trademark vocal style.
Aguilera teamed up with the controversial rapper to write Elastic Love, for her Bionic album, and M.I.A. was looking forward to hearing the pop star belt out the high notes for the song.
But she was stunned when Aguilera decided against it.
M.I.A. tells MTV.com, "Other people were involved who I respect like Peaches and it was like a sea of women coming together to write this new thing. Christina had also had a baby, you know, so it was kind of an interesting situation.
"I really thought I was going to be able to go in there and get her vocals on to the next level and she didn't want to do it. She was like, 'You might think that's great because it's not what you do, but to me I'm really bored of it.'
"It's interesting getting to work with people who can do things vocally that you can't."