When 20-year-old Mackenzie Lesser-Roy auditioned for the role of Girl in “Once,” the college student doubted she’d landed the job.

“I went to the open call on a whim and I actually almost left. I ended up getting a callback. I almost didn’t go to the callback, either because I was just about to start my junior year of college.

“I went to the callback and I had two or three more callbacks after that and then I got a call in the middle of September that they wanted me for the job. It was pretty incredible.” says Lesser-Roy in a phone interview.

Lesser-Roy stars in the eight Tony Awards-winning musical, “Once,” 8 p.m. March 29, 30, State Theatre Center for the Arts, Easton.

“Once” is based on the 2007 film written and directed by John Carney which starred Glen Hansard and Marketa Irglova, who also wrote the music and lyrics. The musical has a book by Enda Walsh.

“Once” follows the complicated relationship of an Irish busker, Guy, and a Czech immigrant, Girl, who meet on the streets of Dublin. Connected by a shared history of heartbreak, they create beautiful music together.

Backed by an ensemble, which doubles as the onstage orchestra, the characters play and sing their way though difficult decisions. Memorable songs include “If You Want Me,” “Gold” and the Academy Award winning “Falling Slowly.”

Sam Cieri, who plays Guy, landed the role during his first theater job, performing on a cruise ship in “Rock of Ages.”

“I sent a couple tapes in and then ended up having to take a private flight out of Bermuda and miss my closing night show just so I could make the audition in New York. I showed up and I completely botched it because I was so tired. But they called me back because, I don’t know, I guess I did an OK job.” says Cieri in a phone interview.

Lesser-Roy and Cieri have strong music roots which prepared them for the music-centered show.

“I’m lucky enough to have had training in classical piano and in classical cello since I was really young. I’ve been in orchestras and choirs my entire life,” says Lesser-Roy. “Coming into this process learning the piano wasn’t too difficult and I had a leg up on the ensemble work. It’s so important to listen to each other and play off each other and I feel like my training has given me an advantage in rehearsing for this show and performing night after night.”

Cieri was playing piano in Las Vegas and busking in New York subways before pursuing theater. He credits having similar life experiences to Guy for helping him tap into the character. “We had a lot in common. We were at the same exact spot. It wasn’t a lot of trying. It was just doing what I was doing and feeling what I was doing.” says Cieri.

Tickets: State Theatre Box Office, 453 Northampton St., Easton; statetheatre.org, 1-800-999-STATE, 610-252-3132