In the first installment of the "battle rounds" the coaches join forces with music industry professionals for guidance. Christina Aguilera teams up with singer/songwriter Sia Furler, Adam Levine with music producer Adam Blackstone, Cee Lo Green with singer Monica, and Blake Shelton with Grammy-winning singer Reba. In this phase the coaches will pit two of their own team members against each other in a dueling duet. After the vocal face-off, each coach, with the help of their adviser, must choose which of his/her singers are the strongest and advance them to the live shows. Carson Daly ("Last Call with Carson Daly") hosts.