Carrie Underwood and Stephen Moyer

Imagine for a moment that it's Thursday at 8pm. You innocently turn on your TV and flip to NBC, thinking maybe you'll catch an episode of Parks and Recreation. Instead, you encounter what is surely destined to be one of the most curious, ambitious and generally nutso undertakings in recent media history: A live (!), three-hour (!!) production of The Sound of Music, featuring country superstar Carrie Underwood (!!!) as Maria von Trapp.

Rest assured, you haven't been smoking edelweiss. This reimagining of the beloved classic about a plucky nun-turned-governess, her irresistible charges and their widower ­father in Nazi-occupied Austria is actually happening on network television — and no one is more incredulous about that than the cast. "I just hope people realize how hard we've worked to do all this," marvels Underwood, who stars alongside Stephen Moyer (True Blood) as Captain von Trapp. "We've really taken on a major project."

That's an understatement. The idea first began with veteran musical producers Craig Zadan and Neil Meron, who were responsible for the film versions of Chicago and Hairspray, as well as NBC's Broadway-themed flop, Smash. "We've always wanted to do something like this, because it feels like, in order to create a real event on TV these days, it needs to be live," Meron says. Drawing inspiration from the 1950s theatrical broadcasts of shows like Peter Pan and Cinderella, the producing pair set out to create a show that's wholly modern and original. Says Zadan, "What we're doing is a hybrid."

The show will be an adaptation of Rodgers and Hammerstein's 1959 theatrical version of the material — not the better-known 1965 film starring Julie Andrews, which is lighter in tone and has fewer songs — performed on soundstages with sets rather than a traditional proscenium. "We would never consider remaking the movie — it is a masterpiece and a classic — but what most people haven't seen is the stage show," explains Zadan. "And we want it to feel cinematic."

Everyone involved is gearing up to spend the full 180 minutes on edge — which is both the lure and the risk of attempting a production of this magnitude. "Every day, I kind of question my sanity," says Moyer with a laugh. "From my personal point of view, saying yes to this was more terrifying than actually doing it will be, considering how big and scary it is."

Of course, preventive measures are being taken to ensure everything goes smoothly — mainly in the casting. The marquee reads like a who's who of Broadway, with five-time Tony winner Audra McDonald (Ragtime, A Raisin in the Sun) as Mother Abbess, Laura Benanti (Gypsy) as the Captain's fiancée, Elsa Schrader, and Smash's Christian Borle as producer Max Detweiler. Moyer, best known for baring his fangs as vampire Bill on HBO, got his start in his native England doing musical theater. And then — oh, yeah — there's that platinum-selling five-time Grammy winner as the lead. "I'm so used to singing live — that's the only way I do things," says Underwood. "I definitely think that will help me come showtime."

The Sound of Music airs Thursday, Dec. 5 at 8/7c on NBC.

For more on The Sound of Music, check out this week's digital version of TV Guide Magazine, available Thursday, Nov. 28!

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