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. That year, the Kidz Bop Kids were named the number one children's music artist by Billboard for the fourth year in a row. However, many of the songs included on the albums dealt with mature themes and featured lyrics that, while not overtly explict or vulgar, were still questionably suited for a very young audience. Along with the expected teen pop fare from Britney Spears, Christina Aguilera, Hilary Duff, and Kelly Clarkson, Kidz Bop included more left-of-center picks like Franz Ferdinand's "Do You Want To?" and Modest Mouse's "Float On" as the series evolved. Along with the regular Kidz Bop collections, which were released roughly twice a year, the franchise expanded to include DVDs and collections of oldies, Christmas songs, and Latin pop hits. Kidz Bop also developed ring tones, toys, and a clothing line over the next few years. The eleventh Kidz Bop Kids album, which featured a cover of Gnarls Barkley's "Crazy" as well as renditions of songs by Justin Timberlake and JoJo, emerged in 2007. Other releases in 2007 included Kidz Bop, Vol. 12 and Coolest Kidz Bop Christmas Ever. The series continued releasing albums every few months for the rest of the decade. ~ Heather Phares, All Music Guide