NEW YORK -- Reuven Gershon and James Fox have some insanely daunting shoes to fill: Every night, they're asked to impersonate John and Paul on Broadway.

Yes, that John and Paul.

Gershon and Fox portray, respectively, John Lennon and Paul McCartney in a Fab Four cover band that has taken its concert show, "Let It Be," from London's West End to New York.

Over two hours, the duo -- Fox is from Cardiff, Wales, and Gershon is from Birmingham, England -- help bang out some 40 classic Beatles songs, from "She Loves You" to "While My Guitar Gently Weeps."

"We have very important jobs because these people will never get to see the Beatles. This is the closest they'll come, so the representation has to be pretty accurate. It's a big responsibility," says Fox. "It's everyone's musical Bible, isn't it?"

They're helping quench an unquenchable thirst for Beatles music that stretches from the Las Vegas home of the Cirque du Soleil show "Love" to fake Beatles bands crisscrossing the nation prompting complaints they're just doing glorified karaoke.

Both men, part of a 10-man contingent cast for Broadway, are singer-songwriters in their 30s with a background in theater who originated their iconic roles in London, even if the program or show never actually identifies them as George, John, Paul or Ringo. Each can sing and play piano, guitar and bass.

"What you have to be good at is being able to replicate what they did," says Gershon, who performs as Frank Sinatra and Dean Martin for birthday celebrations and weddings and has played Buddy Holly in the musical "Buddy" in the West End. "It never ends. There's always more you can do."

As if to add to the pressure, Fox and Gershon are also playing McCartney and Lennon during a lawsuit.

The producers of "Let It Be" are being sued for copyright infringement by the Rain Corp., which produces the rival touring show "Rain: A Tribute to the Beatles." The Rain Corp. claims it laid the foundation for the new production as a "joint author" but hasn't been compensated or credited.

In its lawsuit, the Rain Corp., which brought its show to Broadway in 2010, claims it taught the new group the ropes -- the dialogue, the look of the show, staging, the song list and even the blocking.

Neither show has the rights to tell a behind-the-scenes band story. What they've done is licensed Lennon-McCartney songs -- augmented by no more than two George Harrison tunes per show -- from Sony/ATV, the Beatles' publishing company. They play their set of songs chronologically.

"We tell the story through music and costume changes," says Jeff Parry, a producer long associated with "Rain" who now produces "Let It Be."

Parry says the new show differs from "Rain" in that it was built for a West End theater not a tour, has younger performers than in "Rain" and starts the show at Liverpool's Cavern Club, whereas the rival show begins in 1964 with the Beatles' appearance on "The Ed Sullivan Show."

"There are obviously similarities when you play the music of the Beatles and you do it right," says Parry. As for the number of songs that overlap -- "Let It Be" performs 28 of the 31 Beatles songs that were in "Rain" -- he simply says: "Let's face it, we didn't write any new songs."

Fox and Gershon have come to Broadway from very different places.

For Gershon, "the Beatles were my boyhood favorite band and John Lennon was my boyhood favorite pop star." Fox, instead, grew up a huge Billy Joel fan and got into the Beatles only after becoming familiar with McCartney's solo career.

Gershon, who had already been a Lennon impersonator as part of the band The Counterfeit Beatles, auditioned when his agent found out about "Let It Be." He is making his Broadway debut as part of two five-person casts. (Yes, there is a fifth Beatle: He plays keyboard.)

Fox, who represented the U.K. at the Eurovision Song Contest in 2004 and has had two top-20 U.K. singles, returns to Broadway after playing the Piano Man in the Joel musical "Movin' Out." He got the new job after buying a cheap wig and submitting a video of himself singing "Yesterday."

"I didn't expect to hear back," he says sheepishly.

Parry, the producer, says he and his team looked for musicians with energy. "You have to close your eyes and hear it. We don't go for looks."