This month marks the 40th anniversary of the Woodstock Music Festival's weekend of "sex, drugs and rock 'n' roll," the grandaddy of music festivals, which became an icon of rock music lovers and their counterculture lifestyle.

Now comes another music festival, Ogden's sixth annual A Cappellastock, and one of this year's featured performers, baritone Jeff Peterson, of the host band T Minus 5, makes the comparison. "The name 'A Cappellastock' does correlate to Woodstock simply because it's a big musical celebration with a sense of community, but without quite as much nudity," Peterson quipped. "We play to a family-friendly audience -- no free love, but the feel good part still matches."

Peterson and band members, tenors Jared Allen and Karsten Longhurst, as well as bass Jason "Fish" Salmond and vocal percussionist Shawn Satterthwaite, have created one of Utah's premiere a cappella groups. And family-friendly is right, as the Ogden quintet consists of fathers from their 20s to 40s, with a total of 17 children between them.

All of the singers are Northern Utah natives, who became friends while singing together in Weber State University choral groups. Now the singers perform about 50 times a year for business functions, city celebrations, arts festivals and fund-raisers.

The singers describe their group as a vocal band, distinctive from other a cappella groups by their aim to create a full-band sound -- without instruments -- thanks to their use of electronic special effects. "It's the sound system that really separates us from old-school a cappella," Longhurst said. "It turns Shawn's spitting and popping into kicking and snaring."

Satterthwaite, the group's beatboxing vocal drummer, recreates the sounds of a drum set, but the ensemble isn't limited to those sounds. "You can use your breath and your voice in combination to lay down a beat and get really creative," Satterthwaite said. Even a microphone slapped on the chest can give a percussive beat.

"It's amazing what you can do to manipulate sounds," Longhurst said, "put in a bunch of reverb and add in a lot of low end, and it sounds like a bass drum. Change the EQ on the voices, and it sounds like an electric guitar."

For T Minus 5, its soundman adjusts the equalizer, reverb and distortion to give the voices an authentic instrumental sound, becoming the band's sixth man -- nearly as important any other member of the group.

Satterthwaite arranges many of the ensemble's songs but everyone contributes as they improvise on the compositional "skeleton" he brings to rehearsals. Arrangements evolve from show to show. "That's the beauty of working with talented musicians," he said. "We can just have a jam session on it and come out with beautiful things."

For this year's concert, they plan to debut covers of Michael Jackson's "Thriller" and Robbie Williams' "Let Me Entertain You."

The festival emphasizes music created by the human voice, and in five years has grown to become what promoters say is the largest one-night event of its type, drawing a crowd of more than 2,500.

The show's M.C. will be Las Vegas performer Paul Sperrazza. "My job is to make sure the event runs smoothly and that everybody enjoys themselves," Sperrazza said. "It's all about having a good time."

Three groups will share the stage with T Minus 5, the host band. Blue Jupiter, a group from New York City, is an internationally known pop-jazz-funk quartet of three men and one woman, who won a contest run by American Idol judge Randy Jackson to come up with the best new Oreo cookie jingle.

Mister Tim is a comical one-man-band who uses a pedal to loop his voice so that he can harmonize with himself. The Ogden concert will be one of his first attempts to use this effect in live performance.

Mountain Blue, a bluegrass quartet from Provo, will open the show with their gospel style of music.

One fan of A Cappellastock is Ogden Mayor Matthew Godfrey, who is happy the event found a home in the city's outdoor venue. "It's a cool place to be," he said. "It has a vibe all its own."