Inside Music's Biggest Mash-Up

ALL IN THE FAMILY

Nicole Richie and partner Joel Madden step away from the studio, joining Joe Jonas outside for a friendly chat. Richie's father, Lionel (not pictured), who co-wrote the original tune with Michael Jackson, organized Monday's event along with producer Quincy Jones.

DUET PARTNERS 

8.Nick Jonas leaves his brothers behind and steps into the booth with pop star Enrique Iglesias.