Equally popular and controversial, Razor & Tie's Kidz Bop series of singalong collections debuted in 2001. Known for their "kid-friendly" versions of hit singles that are re-recorded by session musicians and singers and the Kidz Bop Kids, a chorus of child singers, the compilations became popular with families who wanted cleaned-up versions of contemporary songs: 2006's Kidz Bop, Vol. 9 debuted at number two in the Billboard Top 200 album chart, and at the time of the album's release, the collections had sold over seven million copies total.