Iggy Azalea recorded her collaboration with Demi Lovato without listening to the song.

The 25-year-old rap star appears with Demi on the track 'Kingdom' - which features on the singer's upcoming album 'Confident' - and Demi has revealed the unusual backstory to their collaboration.

Demi explained: ''When we finally made the decision of which songs were making the album I said 'OK I want her on this one.' So I called her and was like, 'Hey will you do a song?'

''And she's like, 'Yeah sure I'll go into the studio tonight.'''

Demi admitted to being surprised by Iggy's unusual approach, which helped to solidify her respect for the Australian artist.

Demi told MTV: ''I was like, 'Do you want to hear it first?' She's like 'No it's cool.'''

''I'm like you're an amazing friend and I love you.''

She also claimed Iggy's rap was the perfect fit for the song.

Demi shared: ''I was a fan of her before we were friends, so I feel like I knew what it would sound like.

''And I was just excited to hear it back, it was so much more than I even expected.''