Imagine 50 years of hit music on shuffle, and replace all the instruments with energetic vocalists clad in suits and ties.

Suddenly, you have a Straight No Chaser concert.

Straight No Chaser is an a cappella group created by 10 men in 1996 who were all attending Indiana University. They graduated and went into 9-to-5 jobs, all but leaving their singing careers behind. It all changed when one member, Randy Stine, uploaded a video of the group singing the "12 Days of Christmas" to YouTube. Suddenly, the group was in demand.

Since that day, the group's videos have received more than 20 million views, and they've played more than 160 shows, according to its website.

However, their Thursday, Nov. 14, show at the Knoxville Civic Auditorium was the group's first visit to Knoxville.

"I've talked about going to see them in Chattanooga, but I've never been able to make it there," Allison Miller, who has lived in Knoxville for 20 years, said. "I found out maybe March or April that they were coming to Knoxville and definitely was interested in coming."

Caroline Glaser, a contestant on season four of The Voice, opened the concert.

Before the headliners took the stage, a video was shown to inform the audience on how to watch a Straight No Chaser concert. Major to-do's included dancing, singing along, taking videos or recordings and posting them online to share with other fans.

"I think it is important for people to come out and see true music like this, that has musical value to it," Miller said. "They're not developed talent, not produced talent. They're natural talent on their own.

"What they do is very involved, and it's not auto tuned. That's what I really value about it."

The group performed 17 songs, varying from a mix of Motown favorites like "My Girl" to modern chart toppers, including "I Won't Give Up" by Jason Mraz and the infamous "Blurred Lines." The group also sang original songs, like the "Movie Medley," in which they give famous movie theme songs lyrics, and "Everyday."

One mix in particular elicited a strong response from the audience. It started with "I Will Fly Away," but soon transitioned into an energetic rendition of "Rocky Top."

David Clark, junior at UT and member of Phi Mu Alpha, said his favorite song was "The 12 Days of Christmas."

"That was one of my favorites, too," Sarah Beth Nelius, junior in journalism, said.

"I really liked the Michael Jackson song, and I think my favorite was the one mixed with 'Home,'" Nelius added, referring to "Heard it through the Grapevine" and Phillip Phillip's hit.

Hayley Van Landingham, a fan from Tellico, had a different favorite.

"The last one they did, 'Unplugged,'" Van Landingham said. "I really liked that one."

The audience rewarded the singers with a standing ovation, prompting them to put down the microphones and sing "just as you'd hear it if you walked into the rehearsal hall at Indiana State," member Walter Chase said.

"They passed my expectations," Nelius, who is a member of the UT Singers, said of the show. "Their performance, their stage presence, it was just very well put together."

More information about Straight No Chaser can be found on their website, as well as their Facebook page, Instagram and Twitter. Their music can be found on Amazon and iTunes.