TONIGHT'S MUST-SEE

"Clash of the Choirs" debut, 7 p.m., NBC. Even in a year bloated with reality shows, this might stand out. It has a quick conclusion (six hours over four nights), a feel-good mood and the soaring sound of massed voices. We'll see clips of stars forming choirs in their home towns. There's country's Blake Shelton, plus rock-or-pop stars Nick Lachey, Patti LaBelle, Michael Bolton and Kelly Rowland. Each choir performs one number, in any genre. Then viewers vote and learn Thursday which group won.

"Duel" debut, 7 p.m., ABC. Here's another quick series, covering six nights this week. There are 24 people, including a lawyer, an umpire and an alligator wrestler. Each starts a round with 10 markers and a multiple-choice question. They can mark all four choices, but the wrong markers will be swept away. They can take a chance, but if they don't mark the right answer, they're out.

OF NOTE

"House," 7 p.m., Fox. In a rerun from last season, Vogler is enraged by House's speech and wants him fired.

"Hard as Nails" (2007), 6 p.m., HBO. This documentary focuses on Justin Fatica, an intense, 28-year-old lay preacher.

"Big Bang Theory," 7:30 p.m., CBS. This rerun pairs two former "Roseanne" kids, Sara Gilbert and Johnny Galecki. She plays a fellow scientist, trying to distract him from his attractive neighbor.

"Two and a Half Men," 8 p.m., CBS. Janeane Garofalo guests as someone acting strangely after sex with Alan.

"Great Performances: Rise and Fall of the City of Mahagonny," 9 p.m., PBS. Here is an opera for people who don't think they like opera. The plot is red-blooded, as a sin city emerges in the desert. The words (in crisply enunciated English) emerge from the amazing voices of Audra McDonald, Patti LuPone and Anthony Dean Griffey.

"Journeyman," 9 p.m., NBC. In a new episode, Dan's sister-in-law visits and concludes that he needs help.

"Saving Grace," 8 p.m., TNT. Tonight's story is overwrought, with Grace's sex life possibly becoming an issue in a trial. The season finale, on Tuesday, is much better.

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