There are some moments in history when you might wish to be a fly on the wall, so you could watch and hear events unfold in real time.

In the history of American popular music, one of those moments would definitely be a largely spontaneous jam session that happened at Memphis’ Sun Records on December 4, 1956, when Carl Perkins was scheduled to lay down some tracks; exuberant, up-and-coming piano player Jerry Lee Lewis arrived (hired by Sun founder Sam Phillips) to back him up; Elvis Presley, already hugely famous, dropped by the studio with his girlfriend, just to visit; and Johnny Cash, who’d recently made it big, came at Phillips’ invitation.

You can’t resist wondering what this unexpected gathering of four music icons, in the early days of their careers, crammed into a small studio, was like, can you?

Neither can anyone else. Which is probably how the idea for the stage musical “Million Dollar Quartet,” now being staged at the Encore Theatre, was born.

But because the show’s characters are world-famous rock musicians, the actors who play them must have a skill set that not all musical theater performers have – namely, a rock and roll background. For the actors are also the show’s orchestra (with a couple of additions); and their vocals must be less polished, and more raw.

“A lot of people who do this show – (performing rock music) is another one of their passions, not just musical theater,” said Josh White, who plays Elvis in Encore’s production. “We’ve all been in rock bands, we’ve all played in groups. So we’re in tech week now, and we’re already jamming together, so that skill set definitely plays into it.”

This is one reason that casting MDQ can be tough; and indeed, Encore initially struggled to find the right four lead actors. But once Encore’s audition call was shared on a Facebook page for MDQ alumni (yes, that’s a thing), “one by one, the cast all came together,” said director Tobin Hissong.

Having premiered on Broadway in 2010, MDQ – written by Floyd Mutrux and Colin Escott – altered the factual record in a few ways: Elvis’ girlfriend is portrayed as a singer who occasionally jumps into numbers, as opposed to the dancer she had been in real life; in the show, Phillips expects Cash to re-up his contract with ailing Sun Records that day, though Cash has secretly already signed with another label (in reality, Cash would stay with Sun another year); and the set list for the show (including hits like “I Walk the Line,” “Hound Dog,” “Great Balls of Fire,” “See You Later Alligator,” etc.) differs considerably from the country-and-gospel-heavy original session.

But Elvis’ hit “Let’s Have a Party” – which he recorded a year after the MDQ session – generally sums up the show’s approach and atmosphere.

“A lot of shows have multiple scenes, taking place in different times, where days or months or years are passing, but this one is happening in live time,” said Kaitlyn Weickel, who plays Elvis’ girlfriend, Dyann. “So it’s more about being present in the room, watching it happen in its time.”

And the intimacy of the Encore’s space, according to the actors, will likely only enhance the experience.

“It’ll be a real treat, and feel even more immediate,” said Marek Sapieyevski, who plays Jerry Lee Lewis. “ … I hope to see the walls shaking. I think it’ll be great to do this show in a smaller space.”

Of course, as much as we like to think we know everything about these rock legends, this impromptu Sun Records session happened when Perkins and Cash were only 24, and Presley and Lewis were 21. All except Lewis were “elbows-off-the-table mama’s boys,” said Alex Canty, who plays Perkins. And in terms of their vocal and music styles, as well as their stage personas, they were as-yet unformed.

Which is to say, come expecting to see a shy, polite, Dean Martin-admiring Presley rather than jumpsuit-wearing Vegas Elvis.

“While doing my research, I listened to the first three or four records that Elvis put out,” said White. “And I kept thinking, ‘What? That’s not him. Where’s all the low stuff?’”

Lewis, despite his off-the-charts confidence, was the true new kid on the block. Presley, Perkins, and Cash had toured and played together by the time MDQ takes place, becoming friends along the way (though Presley’s through-the-roof success with a cover of Perkins’ song “Blue Suede Shoes” was a point of some tension); and Phillips was the person who had discovered each musician.

“Jerry came in fully formed, I think, but the others – Sam really shaped their sound,” said Stephen Shore, who plays Johnny Cash. “Carl went from being a backup guitarist and backup singer to singing and playing lead. Sam encouraged Johnny Cash to explore his dark side. And he changed what Elvis sounded like entirely.”

“And Sam wasn’t too much older than these guys at the time, but you get the sense that they found a father figure in Sam,” added Canty. “He had this ability to look into your soul and see what kind of a person you are. Carl’s relationship with his own father had been difficult, so to find someone who was optimistic about what he was doing was just so amazing to him.”

But all four musicians, as well as Phillips, shared a few things in common: they all come from poor Southern families; they were no strangers to tragedy and pain; and they were raised in the Christian faith.

“A lot of them went back to that,” said Canty. “It helped them through what was going on. If you listen to the actual recording of the session, … they sing a ton of spirituals.”

“And loyalty was really important to these guys,” said White. “That’s why the Carl and Elvis situation really stings. These guys live and die by this code of brotherhood. Camaraderie seems like it was more prevalent in that room than ego. They were each starting to grow into their careers, but this early on, they were buds.”

“Million Dollar Quartet” plays at the Encore Theatre (3126 Broad St., Dexter) from Feb. 1-25. For showtimes and ticket information, visit www.theencoretheatre.org.