3.Background vocals on the song "Piece of Me" by Britney Spears are partially sung by Robyn. You can especially hear her on the final robot-voice "You wanna piece of me?" in the chorus.
4.You can hear Taylor Swift mixed with Rihanna's vocals on the song "This Is What You Came For" — in particular, on the chorus "ooohs."
5.Another RiRi one — the person singing that high-pitched chorus "woo-hoo-woo-hoo" on "The Monster" with Eminem is actually Bebe Rexha.