Multi-platinum recording artist Nick Lachey is set to return as host of NBC's upcoming a cappella singing competition series, "The Sing-Off," the one-of-a-kind battle of voices. The show will feature the country's top ten a cappella groups performing popular songs like you've never heard them before. There's no lip-synching, backup bands, or safety net. They'll be singing for America's vote, with the winner walking away with the ultimate prize - a Sony Music recording contract and $100,000.