NBC will premiere “The Sing-Off” Dec. 6 and conclude the five-night musical competition Dec. 20. Each episode will run two hours, from 8-10 p.m.Nick-lachey

Ten a capella groups will compete for a $100,000 prize and a Sony Music recording contract. Three will reach the final episode before a winner is declared.

Last year’s four December telecasts averaged a 2.5 rating in the 18-49 demo, with 7.3 million overall viewers.

Nick Lachey is set to return as host, while judges Ben Folds, Shawn Stockman and Nicole Scherzinger are also back. Last year’s champ, Nota, will return for one of the episodes.

Series is produced by Tenth Planet Prods., Outlaw Prods. and Sony Pictures Television. Joel Gallen, Deb Newmyer and Sam Weisman are exec producers.

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