Bill Champlin isn''t interested in a theory I have professed for several years: that his band, the Sons of Champlin, invented what is now known as acid-jazz. The Sons are the great unheralded whiteboy soul band of the late-''60s San Francisco scene. While the Airplane were fomenting a folk-rock revolution and the Dead were exploring countrified cosmic realms, the Sons set their chops to booty-shakin''. Like Tower of Power, Cold Blood and War-three great East Bay bands of the era-the Sons played jazz instruments and drew inspiration from Motown. But Champlin & Co. spiked their sound with a dose of psychedelia, adding extended jams and wild solos, and preaching a lyrical gospel of hippyistic party bliss.

On the phone the other day, I suggested to Champlin that he may have been the precursor to bands like the Greyboy All-Stars or the Brand New Heavies, who also do the funky-jazz thang. He shrugged the suggestion off.

"We were just playing rhythm and blues," Champlin says, "with a little deeper lyrics. A little bit Marvin Gaye, a little bit Bob Dylan."

As we speak, Champlin is in Las Vegas, a few hours from playing the fifth show in a five-night stand with the band Chicago. He has toured with this version of Chicago-including several original members-since 1982. He has also appeared as a vocalist on 300-or-so albums by more than 100 artists, and won two Grammys for songwriting ("After the Love is Gone," recorded by Earth, Wind and Fire, and "Turn Your Love Around," by George Benson).

But Champlin''s heart remains with his old band. After a decade during which the members pursued solo projects-Champlin most successfully-the Sons reunited around four years ago, and since then have been gigging occasionally, mostly around Northern California.

Champlin is a songwriter/ bandleader/ keyboardist and guitarist, but first and foremost he''s a singer with a powerful, expressive voice. Backing him up in the Sons glory days were guitarist Terry Haggerty, who played complex, jazzy riffs on a big hollow-bodied Gibson, and vibes player Geoff Palmer, who contributed both a jazzy flavor and a trippy tone. Bass player David Schallock and drummer James Preston were a lot funkier than most of the other rhythm sections playing the Fillmore or Winterland back in the day. By the early ''70s, the Sons had picked up a two-man horn section: Tom Saviano on sax and Mic Gillette on trumpet and trombone.

The good news is that almost all of the band-with the exception of Haggerty-will be in Seaside for this weekend''s gig, headlining the day-long Olympic Torch celebration.

"This is no bullshit," Champlin promises. "This is the cats." Champlin says the Sons are in the midst of a renaissance-set to release a new album, and writing new songs. The band has also resurrected what Champlin laughingly calls the band''s "hits"-songs like "1984," "Look Out," "Get High," "Here is Where Your Love Belongs," and a dozen other great songs you have almost certainly never heard.

Champlin is sanguine about the fact that other (lesser) bands became famous while he and the Sons languished in mere critical acclaim and cultish worship.

"When opportunity knocked, we went and answered the phone," he says, laughing.

The City of Seaside has a bit of experience throwing parties on the lawn in front of City Hall, and in Laguna Grande park across the street. Every summer there is a blues series as well as numerous one-time events. But the Olympic Torch Celebration is another thing entirely.

Three or four big trucks will arrive on Canyon del Rey Avenue early on Thursday, Jan. 17. By 4pm., they will have converted the street into a mini-Disneyland. One truck will morph into a big stage, where the Sons and the Torchbearers will appear. Another semi will become "Big Mo," a crystalvision screen showing the Torchbearers in action. A third will transform into an "interactive trailer," where high-tech toys-including virtual reality games for the kids and their dads- will be available.

There will also be world-class hoopla, pomp and circumstance, featuring Torchbearers, skydivers, Olympic Games reps, and fireworks.