The members of Pentatonix: Matt Sallee, Kirstin Maldonado, Kevin Olusola, Mitch Grassi and Scott Hoying. CBS News

"A cappella" means singing without instruments. But we've come a very long way from monks chanting, to Pentatonix, an a cappella quintet that's won three Grammys and sold 10 million albums. YouTube fans have played their videos more than six billion times.

"We've just blended together throughout the years just because of how long we've been together," said Kirstin Maldonado.

And three of the singers—Maldonado, Scott Hoying and Mitch Grassi—have been together a very long time. "Mitch and I were in a show together when we were ten," said Hoying. "I met Kirsti in freshman English when we were 14!"

At their high school in Arlington, Texas, they formed a trio: a soprano, a baritone, and a countertenor. Grassi said of his voice, "It is incredibly high, and it got made fun of a lot while I was growing up. Yeah, growing up in Texas, you know, it was very different and it's a little feminine, so it was like, 'Get him outta here.'"

Hoying said, "Our different timbres make such a specific sound when the frequencies of our voices come together, like they all play such a vital role. When they're all together, it feels like this hug. It's really magical, actually."

In 2011, they decided to try out for NBC's a cappella competition show "The Sing-Off." But when they learned that bigger groups had better chances, they added a bass, Avi Kaplan, and wanted to add a beatboxer. Hoying said, "And so, in an act of desperation, we literally went on YouTube and typed in 'beatboxers.' The first video to pop up was a video of Kevin playing cello and beatboxing at the same time."

It was Kevin Olusola—cellist, singer, beatboxer, and pre-med student at Yale. Asked what his parents had to say when he quit pre-med to become a musician, Olusola replied, "It was definitely not the plan!"

They not only made it onto "Sing-Off," they won the grand prize: $200,000 and a record deal. But within a month, the record company dropped them. Olusola said, "They asked us, 'Hey, will you guys put any instrumentation behind what you all do?' And we said, 'We literally just won an a cappella TV show.'"

Hoying said, "We were just like, 'No, we don't like that idea.' And they were like, 'Okay, then we'll drop you.'"

Instead, they turned to YouTube. Within a year, they had four million subscribers.

"The video that probably really broke us in terms of the industry would be 'Little Drummer Boy,'" Olusola said. "It went to Top 10 of iTunes for four weeks."

The higher the Pentatonix star ascended, the harder they worked. Their behind-the-scenes sixth member, co-founder and producer Ben Bram, wrote ever-more spectacular vocal arrangements. Pentatonix released three albums in 2014 alone, and toured for nine months every year.

"You never got to recharge and be at home, or see your friends or your loved ones," said Maldonado. "It was, like, really, really brutal."

So brutal that, in 2017, Avi Kaplan made a stunning announcement: he decided to take a step back from Pentatonix.

"He didn't really want to tour; he didn't love the tour life," said Hoying. "And we were in our prime and, like, really wanting to tour a lot."

After a nationwide search, Pentatonix found its new bass: a Pentatonix superfan from Maryland named Matt Sallee. "To be able to come into the group and to be able to continue its legacy was something that I cherish very deeply, and I took very seriously," Sallee said.

He was prepared: "I knew everything," he said. "I, like, learned every song, every bass part of every song."

"We were so excited and relieved and grateful that, like, oh, we can see the vision for the future, we can keep this going" Hoying said.

And they did keep going.

I asked, "You guys have been together—living, traveling, working—for years. You can't tell me there aren't things about each of you that drive others of you crazy?"

"Do we have time?" Sallee replied.

"There's a lot. There's a lot," said Maldonado.

Hoying said, "We kind of lucked out that none of us are super-reactive."

"I don't think we all have, like, crazy egos that are, like, getting in the way of being able to communicate clearly with each other," Maldonado said.

But after 14 years in the spotlight, change was inevitable. Olusola said, "Everybody's now starting to get married, have kids. So now, what do we want in this stage?"

What they wanted was to focus on Christmas. Five of their last six albums have all been Christmas music, and their tour is decidedly a holiday show.

And recently, there's been an even bigger change. Their new album, "Christmas in the City," is not a capella! "I feel like it was time to evolve and do something new," said Hoying.

"Because if you put limits on your artistry, then you won't grow," Maldonado added.

But they say they are not abandoning a cappella.

Asked what they think Pentatonix's effect on a cappella has been, Hoying replied, "I think we've made harmony and singing, I feel like we've been part of what made it cool. There's, like, over 1,200 a cappella groups in colleges now."

"Where before people would either say maybe it's nerdy or, like, not cool or whatever," Maldonado said.

Sallee said, "I think Pentatonix really gave the choir kid a voice, a platform to feel seen."

Source