Four tones blend together, moving seamlessly to create a perfect chord. The sound seems to come out of thin air and creates a distinctive ringing as it hits the audience.

This four-part harmony will fill the Englert Theatre, 221 E. Washington St., at 7:30 p.m. Saturday, when the Old Capitol Chorus performs its annual show.

This year’s show has the theme "Good Evening, Mr. Sullivan." The group will sing hits from the ’50s, ’60s, and ’70s.

"It seemed like there were a lot of good musical selections that were entertaining from that time," said Chad Knipfer, the director of the group. "We wanted to please our audience and show them a fun evening at the theater."

The concert will bring the vibe of the classic "Ed Sullivan Show" back to the stage. The men in the chorus will act as employees of the show on break, having a drink and a bite to eat, while also singing a few songs.

"I just hope [the audience gets] a very nostalgic feeling," said assistant director Larry Knipfer, who has been with the group since 1971.

The second act will re-enact the actual "Ed Sullivan Show" portion of the evening with special guests including award-winning quartet Voices Unlimited and the Regina High School choir.

"We brainstormed ideas, and this is one of the few that stepped out as being a bit newer with a little bit different format," said David Keely, the chapter president of the Old Capitol Chorus. "We kind of wanted to diversify the way we entertain."

The a cappella/barbershop group will perform classic songs by the Beatles, the Beach Boys, Simon and Garfunkel, and many others.

Members of the group said what makes Old Capital Chorus work well is the feeling of camaraderie.

"There’s a fraternity that we have with each other," Knipfer said. "My favorite part is the feeling of family, and being able to leave your troubles at the door, and just coming in and having a good time."

Keely said the group is very welcoming to all people, even those who don’t know how to read music but still want to sing.

"I still don’t read music," he said. "But the way we learn songs is we’ll hand out sheets for the lyrics, and online, they have listening tracks so you can hear the arrangement."

There is a diverse background in the group, with people of many different ages and experience levels.

"The basic tie for everyone is you simply like to sing," Keely said. "You’re not trying to be a star singer. The whole point is to blend in with your section and make the arrangement sound special."