Kimbra provides the haunting backup vocals and scatting on this song. The New Zealand singer-songwriter is best known for her contribution to Gotye's hit tune "Somebody That I Used To Know
." Tozer told SonicScoop
how Kimbra's part came together: "We were in the studio together and we played the song for her, and she had a melody idea that she wanted to just quickly record while it was in her head," he recalled. "It was intended that it would be developed and have lyrics written to it, but her scatting sounded so cool, I said, 'let's just use it like that, instead of developing it further.' So what you hear were the original spontaneous ideas that emerged when she first heard the song. It ended up being very cool."