Once the cameraman cued and she began her prerecorded performance on " Dancing With the Stars," though, the fear vanished and that booming voice filled the studio with an acoustic version of Florence + the Machine's breakout hit, "Dog Days Are Over."
Despite performing to an audience more concerned with learning which celebrity would be eliminated on ABC's dance competition, the thunderous standing ovation she received confirmed the power of her voice, a melancholy howl that drifts among blues, rock and soul, and her ability to overcome those crippling nerves.
"Gosh, on live television my legs shake, my arms tremble. My heart was beating so fast," Welch said, seated in a private dining room in West Hollywood hotel the London the following morning. "I find it quite scary. It's definitely something I have to overcome."
The last time Welch was on American television was the first time many on this side of the Atlantic were exposed to her: at this year's MTV Video Music Awards, where her show-stopping performance left many asking just who this upstart Brit was. She scored a prime slot on the show after a team of producers flew to see her play. They asked her to perform on the VMAs immediately following the gig, and she ended up winning one of the four awards she was nominated for.
The raw display of emotion evidenced in that breakthrough performance made her debut album, "Lungs" — a collection of twisted tales of romance woven behind haunting harmonies, guitar strings and tambourine rhythms — a hit back home with fans and critics last year (she even won the Critic's Choice prize at the Brit Awards before the record hit shelves).
"Lungs" debuted at No. 2 on the U.K. album charts and was the biggest-selling release for a new artist in 2009. After it was quietly released in the States last October, her VMA performance yielded a massive sales surge — it shot from No. 44 to No. 14 on the U.S. Billboard 200. The single was inescapable this summer; it played over ads for the film adaptation of "Eat Pray Love" and USA network's "Covert Affairs." That's also her on the ending credits of " Twilight Saga: Eclipse."
The 24-year-old self-described "choir girl gone horribly, desperately wrong" grew up in South London. The product of a chaotic household ("Imagine ' The Brady Bunch' and 'The Royal Tenenbaums' together with lots more swearing," she says), Welch had the freedom to discover a passion for art, English, theater and, eventually, music.
"I'd fallen in love with a boy in a band. I was being dropped off at school in a Sprinter van with half a bottle of Jack Daniels," she recalls in a fit of laughter. "I was getting involved in the punk scene, going to parties dressed in a glittery curtain and getting into Northern soul, Talking Heads, Tom Waits and listening to Etta James and Nina Simone."
Turned on by the chaos of gigging and turned off by art school, Welch began singing by stumbling drunk onto stage during open mike nights and launching into whatever melodies came to mind as she clapped her hands and stomped her feet.
Like most great rock tales, her big break came by happenstance.
While in the bathroom at a club, Welch bumped into Mairead Nash of DJ duo Queens of Noise. Wearing her best tuxedo — it was a phase, much like a witchcraft one as a preteen — Welch did what she did best when intoxicated: She sang, firing off James' "Something's Got a Hold on Me."
"I was bluffing and said I had a band," recalls Welch. Nash called her soon thereafter to book her for a Christmas party. "I told her I wanted to do my own songs and I remember her silence," recalls Welch. Nonplussed, Welch recruited a guitarist and performed three originals.
Despite having never managed an act before, Nash wanted to take her on.
"It was like an instinct reaction," Nash says. "I knew it was the right thing to do. She's an amazing lyricist. There is something about the way she sings, it captures people. It's scary sometimes when you hear her."
Welch, who first thought she needed to join a band or be a frontwoman in someone else's act, went on the road, enlisting friends to back her — a process that didn't go as smoothly as she'd imagined.
"It was like two years of finding the right band and trying to figure out what sound it was [and] we weren't making any money. My dad was my tour manager and we did the MGMT tour in a camper van," she said. "There was a six-month period of no one wanting to sign us."
As for the Machine, it's quite flexible. The backing band can range from being a stripped down set with Welch and a drum kit or piano, or as grand scale as a 75-piece operation complete with a huge choir and strings. At the moment it's a seven-piece collective that includes a harpist, guitarist, keyboardist and drummer.
Welch is gearing up for the rerelease of her debut album, which hits stores Nov. 15. Her lengthy tour concludes with a three-date stint at the Wiltern Nov. 6-8 — though the band will open two dates on U2's tour next summer.
"[Performing] is like getting lost in an imaginary game," explains Welch. "Free of your imagination and dressing up and become whatever character you want to be. I think that's what's really nice about performing. I feel like all the chaos in my brain becomes a bit more clearer when I'm on stage."