"That was so different and unique from what you usually hear in collegiate a cappella that it took a lot of people by surprise," said Stevens.

The CD also has a couple of songs that were selected for national compilation albums, "Sing, Sing, Sing" and "Super Mario."

"We're very excited to be on those albums," says Stevens. "Hundreds of groups submit songs for those."

Other signature pieces on the CD include "Thriller" and "Sunshine Medley," two songs called "Home" (one by Michael Buble and the other by New Orleans native rocker Marc Broussard). There's a tribute to "Forever Plaid" with "No Not Much." There's a version of "Black Balloon" that "people tell me they can't tell the difference between that and the radio," says Stevens. Plus, the groups celebrate their "Sunday side" with a couple of hymns, "Praise to the Man" and "Nearer My God to Thee."

"People sometimes ask why we don't do an all-hymn collection," says Stevens. "But we want the CD to mimic the concert experience, to share a variety of music. We'd never do an all-pop or all-rock CD, either."

What he particularly likes about this CD, he says, is that "it appeals to all ages. We hear about kids that listen to it 'nonstop' (pun intended), but we also hear from older listeners. It transcends generations. Whole families can listen together."

There's something about a cappella music in general that does that, he says. It has become increasingly popular in recent years.

"It has always been popular with collegiate groups on the East Coast, but in the past 10 years, it has become hip and cool everywhere," says Stevens.

That increasing popularity, he thinks, has come because a cappella music "breaks the barriers. It's a heart-felt way of performing. You hear echoes of revival singing. There's nothing reserved about it. You're not hiding behind a guitar; you have to just stand there and sing. But that creates a connection with the audience."

The very things that make a cappella so popular, however, also make it difficult. All the sounds are created by the human voice, and although the songs you hear on the CD may make you think there is a whole orchestra backing them up, that is not the case.

"We don't have a band to help us keep the tonality," says Stevens. "We have 9 different voices that have to stay on pitch while they are all singing different parts. That's not so hard when you only have four-part harmony, but we routinely throw in seven-part and nine-part harmonies and do it quite randomly."