“The Sing-off” (8 p.m., NBC): “The Sing-off” sounds like “American

“The Sing-off” (8 p.m., NBC): “The Sing-off” sounds like “American Idol”-lite. It’s a four-night reality series in which a capella groups will compete for $100,000 and a recording contract. Nick Lachey hosts.

“Jennifer Hudson: I’ll Be Home for Christmas” (8 p.m., Fox): In the hourlong special, “Jennifer Hudson: I’ll Be Home for Christmas,” the singer and actress relives her childhood holidays in Chicago by performing at her small neighborhood church and other locales.