MUSIC : Still in Harmony : The New Four Preps, including founding members Bruce Belland and Ed Cobb, will perform at the Academy Plaza Theater. The group has found niches with both young and old.

The old blazers with the embroidered crests were abandoned long ago. And the blond Ivy League haircuts have, in some cases, receded with time. But the smooth harmonies that earned the Four Preps a string of hits in the late ‘50s and early ‘60s survive.

The quartet is today called the New Four Preps, and still includes founding members Bruce Belland and Ed Cobb, who launched the act at a Hollywood High talent show back in 1955. And before the Beatles emerged in 1964, forever changing the creative boundaries of pop and rock music, the Four Preps enjoyed such lingering hits as “26 Miles,” “Big Man” and “Down by the Station.”

The four-part harmonizing on the Southern California lifestyle in those songs was a key influence on such later acts as the Beach Boys and Jan and Dean. Their clean-cut, preppy image dogged the group through most of its career, although Belland now jokes: “We’ve managed to counteract that now. We’re just dirty old men.”

The New Four Preps, who will perform two shows Sunday at the Academy Plaza Theater in North Hollywood, include members of such chart-topping acts as the Association and the Diamonds. Tallied together, the new act’s four members have created 29 hit singles, from the Association’s “Cherish” to the Diamonds’ “Little Darlin.’ ”

“I don’t think any of us would have gone back out on the road and busted our humps with the one-nighters, sound checks and all the hassles that go with traveling, if not for the exciting prospect of singing with this kind of talent,” says Belland, 56.

“We swap solos around. And it becomes in some ways sort of improvisational and ad-lib. We try to surprise each other.”

The Preps re-formed in the ‘90s with the intention of playing mostly black-tie dates at corporate conventions, and they have enjoyed much success on that circuit during their usual 50 to 65 dates a year. Many of their original fans have since become business executives, says Prep member David Somerville, 60. “They grew up on this music. They can afford whatever they want now, and they want their music, damn it.”

But the new group, which also includes Jim Yester of the Association, has also discovered that their appeal extends to family festivals and such high-profile club venues as Trump Castle in Atlantic City, N.J.

“The oldies stations, bless their hearts, keep this stuff alive,” says Somerville, an original member of the Diamonds, who joined the Preps in the ‘60s. “A lot of children hear this music.”

Belland is quick to note that the new group is much more musically sophisticated than the quartet of teen-agers that founded the Preps. After all, each of the New Four Preps has since earned long resumes in the music and entertainment industry.

“There is no comparison,” Belland says. The new act’s performances are accompanied by five live musicians and occasional taped orchestral elements, for a repertoire that includes a 20-minute medley of the members’ top-10 hits, and several popular songs by Elton John, Mariah Carey, the Beatles and Chicago.

Some of that material has emerged on more recent recording projects, such as last year’s “Better Than Ever” album. Another album, titled “We Be 50,” was just completed.

The North Hollywood concert marks the first time any version of the Four Preps has performed in the San Fernando Valley, even though Belland has spent most of his adult life in Encino, and both his daughters attended Birmingham High School in Van Nuys.

“I’m hoping some old friends are going to show up,” Belland says.

WHERE AND WHEN

* What: The New Four Preps.

* Location: Academy Plaza Theater, Academy of Television Arts and Sciences, 5230 Magnolia Blvd., North Hollywood.

* Hours: 5 and 8 p.m. Sunday.

* Price: $15.50 and $21.50.

* Call: (818) 785-8885.