H.O.R.D.E. Sweeping West With Tour : Pop music: A growing concert phenomenon will stop at Irvine Meadows on Saturday for an all-day festival with performers in the jam-band tradition.

Like the original horde commanded by Genghis Kahn, the H.O.R.D.E. Festival is about to reach its goal of galloping across an entire continent.

The festival’s all-day encampment at Irvine Meadows Amphitheatre on Saturday--with the Allman Brothers, Big Head Todd & the Monsters and Blues Traveler forming an instrumentally adventurous vanguard at the top of the bill--marks the West Coast debut of a phenomenon that has been growing since the first H.O.R.D.E. (Horizons of Rock Developing Everywhere) tour in 1992.

“The first tour was basically just a group of friends getting together and deciding to do some dates,” Blues Traveler’s manager David Frey said of that two-week jaunt along the East Coast. It involved Blues Traveler and Spin Doctors, brother bands that emerged from the same high school in Princeton, N.J., as well as Phish and Bela Fleck & the Flecktones.

Last year H.O.R.D.E. gained in numbers and range in a 25-city tour by Blues Traveler, Big Head Todd and other bands with an allegiance to the jam-band tradition established by such ‘60s and early-’70s forebears as Cream, Traffic, the Mothers of Invention, the Grateful Dead and the Allman Brothers.

This year’s H.O.R.D.E. spreads to 32 cities and acknowledges that tradition with the reinvigorated ‘90s version of the Allmans in the headlining spot. Opening for the Allmans, Blues Traveler and Big Head Todd, Sheryl Crow lends a female presence and a singer-songwriter sensibility to the proceedings.

Like “Lollapalooza,” H.O.R.D.E. features a midway-style concourse with such attractions as a virtual-reality “LSD flight simulator,” an exhibition of Jimi Hendrix memorabilia, arts and crafts booths, forums for social action and political organizations, and, for the physically adventurous, a bungee trampoline and a surfboard variation on the old mechanical bull.

Also like “Lollapalooza,” H.O.R.D.E. will expose less-established talents, who will play 30-minute sets on a concourse stage. The newcomers, in order of appearance, are the 2 P. C., Jambay, Ugly Americans, Cycomotogoat, Screamin’ Cheetah Wheelies and April’s Motel Room.

The tour’s producer, Peter Barsotti of Bill Graham Presents, points to a promising innovation improvised a week into the H.O.R.D.E. itinerary: workshop performances featuring some of the artists.

Barsotti got the idea from working on this year’s version of Peter Gabriel’s WOMAD festival. The H.O.R.D.E. workshops were launched last week at the Chicago festival site. Blues Traveler’s John Popper gave a blues harmonica demonstration, with help from Sheryl Crow and members of her band and the Screamin’ Cheetah Wheelies. Allman Brothers percussionists Jaimoe and Mark Quinones gave a drum workshop.

“We’re going to do it every place (on the tour) where we can find three sonically isolated spots” that will permit a workshop stage that won’t be drowned out by main-stage and concourse-stage performances, Barsotti said. That could be a challenge at Irvine Meadows. “I’ll make it work somehow,” he vowed. “There’s something about being up close to the performers and being able to talk to them that makes it special.”

* H.O.R.D.E. on Saturday at Irvine Meadows Amphitheatre, 8800 Irvine Center Drive, Irvine, (714) 855-4515. $30 and $22.50. Times for the main performers: Sheryl Crow, 2 p.m., Big Head Todd, 3:15 p.m., Blues Traveler, 5:15 p.m., Allman Brothers, 7:30 p.m. Second-stage performances begin at 12:30 p.m.