David Alan Grier loosened up by joking around in a faux Shakespearean actor voice.

Limber dancers in creature costumes, ranging from furry winged warriors to sexy poppies to sassy crows milled around the edges of the stage, where members of the off-stage chorus gathered around a rack of headphones to wait for their cues. Shanice Williams, the bubbly ingenue of NBC’s “The Wiz Live,” was primped and hugged and quizzed about when she ate last in the moments before the start of Wednesday night’s final dress rehearsal.

If “The Wiz” team was feeling the pressure leading up to tonight’s live telecast, they weren’t showing it. Wednesday’s runthrough went smoothly and clocked in on time, a big concern for a network with any live event.

“Wiz” is the third live musical event that NBC has staged under the leadership of NBC Entertainment chairman Bob Greenblatt, who has moonlighted as a Broadway producer periodically during his long career in TV. Shepherded by director Kenny Leon and exec producers Craig Zadan and Neil Meron, “Wiz Live” is a reimagining of the 1970s Broadway musical that put an R&B spin on the enduring “Wizard of Oz” story.

NBC’s 2013 production of “The Sound of Music” shocked the TV biz by delivering 18 million-plus viewers. Last year’s “Peter Pan Live” was less successful from a ratings perspective, but still a buzzy event for the network. The “Wiz” is seen as having bigger potential as it is a more familiar musical property to audiences than “Peter Pan.”

It’s also aided by deft casting, including: Queen Latifah as Oz, Ne-Yo as the Tin Man, Mary J. Blige as the Wicked Witch of the West, Uzo Aduba as Glinda the Good Witch, Elijah Kelley as the Scarecrow, Grier as the Cowardly Lion, Common as Oz’s Bouncer gatekeeper and Amber Riley as the Wicked Witch of the North. Williams, a 19-year-old New Jersey native who was plucked from an open audition, rises to the occasion with stage presence and vocal chops that soar beyond her years and limited professional experience.

Once again, NBC’s one-night-only musical is originating from a soundstage on the Grumman Studios lot in Bethpage, Long Island. The magnitude of the production is evident in the number of satellite trucks, trailers and heavy machinery parked outside the stage. Inside, the backstage area looks like a Broadway production writ large.

“Wiz Live” is a more elaborate production than the previous two tuners, with a bigger investment in costumes, sets and choreography. But the journey from Kansas to Oz and back again will play out on a single stage (compared to three for “Peter Pan” and five for “Sound of Music”), thanks to the cutting-edge magic of rear projection of scenery on giant LED backdrop screens. From the opening scene that finds Dorothy and Auntie Em (played by Stephanie Mills, the original star of Broadway’s “Wiz”) in a wind-blown field of wheat, the effect is visually engrossing.

The backstage area is positively electric. In the hangars where Grumman once built machines for aerospace and defense purposes, dressing rooms have been cordoned off with scaffolding and velvet drapes for the stars. There are dedicated dressing areas for the players in most of the 18 musical numbers, which are enlivened by the eye-popping, boldly colored creations of costume designer Paul Tazewell. Tazewell began working on “Wiz Live” nine months ago after setting the sartorial tone for the Broadway smash “Hamilton.”

The makeup artisans who run the prosthetics room, headed by the husband-and-wife team of Dave and Lou Elsey, function like a pit crew at a racetrack. Grier, Kelley and Ne-Yo have less than 20 minutes to transform themselves into their main characters after performing the opening scene in Kansas farmhand duds. When rehearsals first began in October, the process of applying the Lion, Tin Man and Scarecrow costumes and makeup took some three hours.

In the middle of all this is a warren of vanity mirrors and dressing tables where dozens of dancers and background cast members are prepped for their numbers. Next to that cluster is a necessary element for any show involving that many dancers and acrobats — a large open space for stretching, dancing, voguing and general tension-relieving horseplay prior to the curtain. Cirque du Soleil has loaned “Wiz Live” a host of rubber-limbed performers who are used to great effect by director Leon and choreographer Fatima Robinson, starting with the human tornado that sends Dorothy on her way to Oz.

Surveying the backstage scene, Greenblatt, sporting a maroon “Wiz Live” hoodie to guard against the chilly temperature on the stage, notes that a soundstage offers far more elbow room backstage than a typical Broadway effort. “We’d be holed up in tiny spaces in most theaters,” he said. “This makes it feel really big.”

Big it is — complete with pyrotechnics, multi-story sets and a giant menacing mechanical head as befitting Oz the Great and Powerful. Dozens of set pieces are trucked on and off the stage by a swarm of crew members who are frequently moving around on the stage while the actors are performing. Unlike a live theatrical production, the only frame that matters is what the TV cameras capture, which allows for the needed flexibility to set up the ensuing scenes. It takes a slew of fast-moving hands to tape down the Yellow Brick Road in time for Dorothy and her pals to ease on down.

In a first for a non-sports live TV event, “Wiz Live” will air with a video description track designed to allow visually impaired viewers to follow the telecast. The track, available on the SAP channel feed offered by NBC’s affiliate stations, will be delivered live by a narrator who will stand just offstage. He or she will have to talk fast because “Wiz Live” is a visual feast.

Nobody has more riding on tonight’s performance than Williams. The young actress is living a “42nd Street”-esque dream of emerging from an open call audition to a gig that may very well launch her to stardom. Her first major public performance — outside of community theater — came last week during the “Wiz Live” number that was featured as part of NBC’s Macy’s Thanksgiving Day Parade telecast.

Among Williams’ champions during the past six months has been Allison Williams, the “Girls” star who took flight last year as the title character in “Peter Pan.” On Wednesday, Allison sent a gigantic box of Dylan’s Candy Bar goodies for the entire “Wiz Live” cast — with special emphasis on yellow jelly beans, of course — and a big bouquet of flowers for Shanice.

Given her circumstances, it’s no surprise that Williams’ Dorothy sheds real tears during the penultimate musical number when Aduba, who makes a suitably grand entrance, belts out one of the tuner’s showstoppers, “Believe In Yourself.”

At the end of Wednesday’s dress rehearsal, Williams stepped off stage into the open arms of vocal coach Liz Caplan, who gave her a bear hug that lasted several minutes.

Cast and crew members exchanged high-fives, handshakes and back-slaps and generally exhaled after three hours of hard work against a ticking clock. Zadan, Meron, Greenblatt, Leon, Robinson and other key players had little time to unwind before the stage manager’s voice boomed over the PA system, calling all department heads back to the stage for a fix-it and fine-tuning meeting.

By the time they all regrouped, the 24-hour countdown to tonight’s telecast had begun.