1. Let's start with a classic: Justin Timberlake is the one singing the chorus of the Black Eyed Peas song "Where Is the Love?" and not Fergie.

2. John Legend sings background vocals on the song "American Boy" by Estelle featuring Kanye West. He even pops up in the music video.

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.

6. In the stripped-back chorus near the end of Bleachers' "Don't Take the Money," you can clearly hear Lorde singing with Jack Antonoff.

7. Charli XCX, who is one of the writers of the track, is clearly singing on the chorus of the Selena Gomez song "Same Old Love."

9. Ashanti can also be heard all over the J.Lo songs "Ain't It Funny" and "I'm Real."

10. Pharrell, who is also a producer and writer of the song, is the one singing background vocals and the chorus in Kendrick Lamar's "Alright."

11. You may have noticed a woman's voice on "Club Can't Handle Me" by Flo Rida feat. David Guetta — well, it's none other than Nicole Scherzinger.

12. Finally, you can clearly hear Ed Sheeran on the chorus of the Justin Bieber hit "Love Yourself."
