NEW YORK, NY.- In high school, I joined Rebel Yell, an a cappella group named after the Billy Idol song. I mostly beatboxed or sang background vocals. But one year, my chorus teacher gave me a lead vocal.

It was on a song called “Insomniac,” by a folk rock duo called Billy Pilgrim. Our audiences didn’t know the song before we sang it. None of us did, which made it an odd choice for contemporary a cappella, where most of the songs performed are big hits. I didn’t realize until years later that groups all across the country were singing this song, without knowing anything about the original version.

But why?

Two students at Emory University, Kristian Bush and Andrew Hyra, formed Billy Pilgrim in the early 1990s, and their self-titled major record label debut came in 1994. “Insomniac” was released as a single, but never charted. The band, named for the lead character in the Kurt Vonnegut Jr. novel “Slaughterhouse-Five,” didn’t collect much acclaim either.

The duo stopped playing together in 2000. Bush formed Sugarland with Jennifer Nettles, and his music career took off. Hyra became a carpenter.

However, the strangest thing happened with “Insomniac.”

It took on a life of its own. For almost three decades, the song has been a staple of a cappella groups all over the country at all levels, whether high school, colleges, professional groups or otherwise.

Go on YouTube, and you’ll find countless performances of the song through the years. A sampling: The professional group Straight No Chaser. Ow! at Glenbrook North High School. Section 8 at Ohio University.

Amid the roster of popular songs typically selected by a cappella groups, “Insomniac” stands out as an unusual favorite. Alex Kaplan, a 20-year-old junior at Wesleyan University, said he performed the song with his group, the Wesleyan Spirits, “a couple days ago.”

“It’s not uncommon for the occasional song to sort of gain a foothold in the a cappella community if it’s got particular qualities that lend themselves well to performance,” Kaplan said. “‘Insomniac’ is a weird one because it’s, with maybe one or two exceptions, just about the most unknown song that I’ve seen multiple a cappella groups do.”

It is a melancholy, guitar-driven love song, with lines like, “I can hear your bare feet on the kitchen floor/I don’t have to have these dreams no more.”

The recording begins with a wailing Hammond organ and the middle of the song has a musical interlude, which extends into a jam of sorts. Emily Saliers of the Indigo Girls sings background vocals on the Billy Pilgrim version.

“I was looking for a girlfriend,” said Bush, the song’s writer.

The path for “Insomniac” becoming ubiquitous in the a cappella world began before the record was even released.

In the early 1990s, a cappella — singing without instrumental accompaniment, with the sheer power of the human voice — was changing.

Groups such as Rockapella and The Nylons were ushering in a new mainstream approach, different from the traditional barbershop quartet style of many predominantly white male groups of the time. This newer style of performance meant that every instrument on a given song was accounted for. Drums would be represented by beatboxing, guitar strums and piano chords represented by rhythmic vocal approximations.

Deke Sharon, an a cappella-obsessed student at Tufts University, also helped pioneer the shift, particularly on college campuses. As musical director for the Beelzebubs, the Tufts group, he encouraged previously unperformed arrangements of pop songs. After graduating in 1991, Sharon aimed to make a career spreading the gospel of a cappella.

“Everybody laughed,” he said. They said, “You can’t make a career out of a cappella,’” but he said he told them: “It’s so wonderful. If people only knew, they would literally fall in love.”

There wasn’t much recorded a cappella before that, except for occasional exceptions such as Bobby McFerrin’s “Don’t Worry Be Happy” or the Huey Lewis and the News cover of “It’s Alright.”

Sharon formed a nonprofit called the Contemporary A Cappella Society, with the aim of popularizing this new, more modern form of vocalizing through a cappella festivals, awards shows and networking events for enthusiasts.

He also had an idea. Back then, college groups had no way of spreading their music beyond campuses. There was no YouTube or Spotify. The web had yet to arrive, and even email was uncommon.

Using a meticulously crafted database of groups that he had compiled in his dorm room, Sharon started taking submissions for “Best Of College A Cappella” compilation albums. Groups that made the cut would be on a compact disc that they could sell at shows. They could buy them for $5 and sell them at shows for $15. Suddenly, a performance from, say, Rutgers University, could be available at Boston College.

It was around this time that John Craig Fennell, a graduate student at the University of Virginia, joined the Virginia Gentlemen, an all-male offshoot of the Virginia Glee Club. Working at a summer camp in New Jersey, a co-worker handed him the newly released Billy Pilgrim debut.

“You hear those first few squeezebox notes on the Billy Pilgrim track,” Fennell said. “I love it. it was immediately compelling.”

He saw an opportunity to take advantage of the shift in a cappella and stretch the abilities of the Virginia Gentlemen. He painstakingly transcribed the arrangement by hand — how most arranging was done back then — with voices emulating the sounds of the guitar and organ: “JUM-BUH-DUH, JUM-BUH-DUH.”

The arrangement marked one of the first times that all 14 members of the Virginia Gentlemen had their own vocal part on a song, he said.

They submitted their recording to Sharon, who liked it enough to put it on one of the first “Best Of College A Cappella” albums in the mid-1990s.

From there, the record hit campuses and the arrangement began to spread the old-fashioned way: word-of-mouth.

Other groups copied the arrangement by ear. A member of the Wesleyan Spirits who had performed a version in high school brought it to the Spirits. That arrangement made its way to the Vineyard Sound, a group based on Martha’s Vineyard. Similar arrangements were performed at the University of Rochester and Plymouth State.

“This song is what made me fall in love with my group,” said Michelle Shankar, who was part of the Dartmouth Dodecaphonics from 2008 to 2012. “They open almost every show with this piece. It’s high energy, super upbeat, at least the a cappella version of it is. And it just starts with this wall of sound — that really high belt that’s like, ‘Whoaaa!’, and that just became an iconic line.”

Many of the singers interviewed about the song could not help but sing a few bars, unprompted.

“It’s a perfect storm that is specific to ‘Insomniac,’” said Walter Chase, a founding member of Straight No Chaser.

Chase arranged a version after hearing it off the compilation album for the group in the mid-1990s, when it was still a college group at Indiana University: “When you’re a college student and one of the main purposes you do a cappella for is to sing for girls, to get attention and to be able to croon, the soloists’ material is this very heady love song.”

On an annual retreat in Atlanta around 2000, the Wesleyan Spirits performed the song at a bar during the day. The bartender informed the group that it just so happened that Bush, the song’s writer, happened to be performing that same night. The Spirits returned that evening and Bush invited the group onstage to sing his song.

“I remember trying to play it, and it was very square,” Bush said, laughing. “You can’t really play guitar to it.”

Still, Bush and Hyra had little awareness of the niche hit they had created. Hyra first realized it about a decade ago when he was sitting at a hotel in Martha’s Vineyard with his family, including his sister, actress Meg Ryan.

The Vineyard Sound were nearby and began to sing “Insomniac.”

“I was like, ‘Holy cow!’” Hyra said.

Ryan, who still calls herself Billy Pilgrim’s No. 1 fan, said she couldn’t believe her ears.

“I’m not a singer, but I can always sing along with that song,” the actress said. “They always seem to write these songs that kind of give poetry to something very universal.”

With the help of movies like “Pitch Perfect” and the former NBC show “The Sing-Off,” a cappella has gone more mainstream. Production values are higher, and transcription is easier using software. But the Virginia Gentlemen’s arrangement of “Insomniac” remains a constant.

Billy Pilgrim reunited during the pandemic. The band has never made any money off the covers, but the song’s spread has left them elated. At concerts, “Insomniac” is their most requested song, Bush said. They even perform a new version.

“Maybe that song should have been a big hit,” Hyra said.

Bush finds the whole phenomenon delightful.

“The music business is a whole series of ‘You’re already failing,’” he said, adding, “Every once in a while, something shows up and it ties a little balloon to your belt loop and suddenly you’re a little lighter, you know? And I think that’s what this does for me.”

This article originally appeared in The New York Times.