"These nights are my favorite nights living in New York," says Corey Mach.

Mach is the creator, producer and brain behind the popular Broadway Sings… concert series, evenings that gather a handful of theatre's best singers to cover Billboard-topping hits by renowned pop artists—but with a theatrical flair. He's gearing up to return to the Highline Ballroom Feb. 22 for another epic night in New York with Broadway Sings Billy Joel, the tenth installment in the series.

It all began in 2011, when Mach was a standby in the Broadway revival of Godspell. Tony Award voters were attending the show, so most of his time was spent in the Circle in the Square dressing room—as the principal players made sure they were seen during the crucial time leading up to the awards ceremony.

"I needed something creative to work on," he explains, "and I've always been really good about creating my own stuff—when nothing's happening to make it happen for yourself. My school [Baldwin-Wallace University] was a huge advocate of making sure you did that once you moved to New York."

He met his musical director and arranger, Joshua Stephen Kartes, at an open-mic night in which Kartes was able to transpose a Jason Robert Brown tune down a step in a pinch. "I wasn't feeling well," Mach explains, so "he played 'Moving Too Fast,' one of the hardest songs to play on the piano in musical theatre history, down a step with no music. And I was like, 'Get out of here! I've been playing piano for like 25 years, and I know how hard that is.'"

The two began collaborating, and Broadway Sings… kicked off with a tribute to Adele, the Grammy-winning star who recently resurfaced with the new album 25. Godspell castmates Eric Michael Krop, Julia Mattison and Morgan James, as well as Matt Doyle, Brandon Victor Dixon, Asmeret Ghebremichael and others joined Mach in the inaugural concert.

"It went so well that the performers each individually came up to me after and said, 'You have to do this again; this was a blast!'" says Mach. "And a lot of the audience was really into it, they were asking, 'When's the next one?' so I had nothing to do but do it again."

Each concert got bigger and better—Mach filled out the band, adding a horn section and additional strings, as well as bringing on more cast members. Broadway Sings Billy Joel boasts a cast of 24, ranging from Into the Woods star Lilla Crawford to former Broadway Elphaba Christine Dwyer.

"I pick the artist based on what I like at the moment," he explains, "and that usually ends up being an artist that is really present right now. We did Bruno Mars when he had just done the Super Bowl. Billy Joel's now doing his Madison Square Garden residency, [so] I try to pick a current artist who's really hoppin' right now. I feel like at the time we do each concert, I'm obsessed with each artist at that time."

What makes the series special, though, are Kartes' re-imagined arrangements. A month before each show, Mach and Kartes sit down with each singer for about an hour to toss around ideas.

"If Alysha Umphress comes in—she's an amazing scatter—we would take an Amy Winehouse song and completely turn a ballad into an up-tempo jazzy arrangement that still honors the song, but makes it into something really special for that singer. Or, we'd take an upbeat Stevie Wonder song and bring Matt Doyle in and have him do a pretty Jason Mraz ballad-y version of it. That's kind of our process. We record that whole session, and then the next time we see the singer is the day before the show where we bring the whole band together."

As a producer, "it's totally my side job," says Mach. The day after one Broadway Sings… concert ends, he begins work on the next—no matter what projects he has lined up as a performer. (He was in rehearsals for Invisible Thread when Broadway Sings Sara Bareilles was taking shape and had to come home from Boston when he was doing Waitress to do the Broadway Sings Bruno Mars concert.)

As the series grows, Broadway performers jump at the chance to sing. "I have people now in this [Billy Joel concert] who asked a year ago to be in the concert at some point… I've kind of mastered how to bring as many [audience members] there, so that I can get some extra money to pay the entire band how they'd like to be paid and to pay 24 performers as well."

The pop artists are taking notice as well. Bareilles is a friend of Mach's, having worked with him on the world-premiere production of Waitress (and she had nothing but good things to say), P!nk and Bruno Mars tweeted the group, and Justin Timberlake sent Mach and the cast four dozen white roses to Feinstein's/54 Below. ("I thought I was being punked," Mach jokes.)

On the bucket list for Broadway Sings… are tributes to Whitney Houston (the next in the series following Billy Joel), John Mayer, Jason Mraz, Queen and Celine Dion. Mach also hopes to start recording the shows in their entirety as albums, so that the music lives on beyond YouTube.

(It should be noted that the Broadway Sings… concert series is separate from the Broadway Loves series, which covered Celine Dion at 54 Below, and the Broadway Rocks series.)

Of course, it would be nice to get a pop star or two in the house. "I hope to get to the point where they become so big that the [tribute] artists have no choice but to come," he says. "That's the ultimate goal—to have the artist at the show, and to have them hear their songs sung in a completely new way."