Let’s say it’s 1982, and the members of Ambrosia have just gone their separate ways. What if someone had told bassist-vocalist Joe Puerta that 18 years later Ambrosia would be on the same bill as Dave Mason, Gary Wright and Al Stewart for a Class of the ’70s tour, opening Dec. 10 at the Radisson Hotel in Sacramento? What would be his reaction?

Amazingly, Puerta – also a founding member of Bruce Hornsby and The Range – doesn’t scoff at the thought.

“I would try to keep an open mind about it, in a realistic view,” Puerta said recently from his new home in Wisconsin. “I think one has to realize that musical tastes change, and that what you’re doing isn’t always going to be popular with big consumers. The kids out buying ‘N Sync, Christina Aguilera, whoever, aren’t going to be interested in Ambrosia and Gary Wright and Al Stewart, but there’s a large group of people that grew up on our music. That’s who we’re still playing for. What’s interesting is that some of their kids are coming to the shows.”

A devoted audience still remains for the theatrical prog-rock of “Holdin’ On to Yesterday” and “Nice, Nice, Very Nice” and the laid-back pop of “How Much I Feel,” “Biggest Part of Me” and “You’re the Only Woman (You & I)” – even if lead singer David Pack is too busy with other commitments to come along for the ride.

“His career has taken off as a producer and he sort of bowed out of the live shows,” Puerta said. “He shows up once in a while; I kind of liken it to Brian Wilson and the Beach Boys, when Brian got more oriented toward the studio stuff and live shows became too difficult for his schedule. It’s pretty hard to work the projects Dave has going and say, ‘Hey, when you’re done with this, you’re flying out of the airport and you’re going to be gone all weekend, you get back home on the red-eye and you’re back in the studio on Monday.’

“We’ve left the door open so if Dave can make it, great, but we’ve worked around it for so long we’re comfortable doing the live shows around Dave.”

Pack has produced Wynonna, conceived and produced the all-star tribute album “Songs From West Side Story,” has collaborated with the Rev. Billy Graham and regularly works with Christian artists.

Puerta, keyboardist Christopher North and drummer Burleigh Drummond carry on in Pack’s absence, using three other musicians to augment their part-cerebral, part-soft-rock sound. They’re able to pull it off because, whether fans are aware of it or not, Puerta was just as much a featured singer in Ambrosia as Pack.

“Dave and I sang together for so many years that a lot of times people don’t even know we’re switching off,” Puerta said. “On ‘Nice, Nice, Very Nice,’ for example, we both sang lead. We switched back and forth.”

Ambrosia also has made a comeback in the studio. The group, including Pack, has worked on demos for their first album since 1982 and were signed to Miramar Records, which also had deals with Stewart and Alan Parsons. But Puerta said, “After we signed with them, their parent company subsequently went into Chapter 11. We were ready to start a record and this happened and now we’re in limbo.”

Ambrosia’s career was unconventional from the start in 1971 when Los Angeles Philharmonic conductor Zubin Mehta inadvertently put them on the path toward a major-label deal.

“When we were a young band, we were living out in Hermosa Beach, Calif., and a friend of ours had a sound company,” Puerta said. “They called us up and said, ‘You guys want to play the Hollywood Bowl?’ We were like, ‘Yeah.’ ‘Here’s the deal, we need to sound-test our system there. It’ll be on a Sunday afternoon and there won’t be anybody there.’ We did that, and there was this classical engineer named Gordon Perry, one of the most famous engineers in the world. He’s won five Grammys. He came up to us after the sound check and said, ‘I stopped listening to the system and started actually listening to your music. It sounded very good. I’d like to invite you guys here anytime.’ We started showing up at the Bowl just about every night; somehow we started meeting people like Zubin Mehta.

“(Perry) put together a concert to kind of showcase us, and Zubin Mehta came to the concert. After Zubin saw the show, a piece came up a few months later where they needed a rock band to play with the orchestra. So Zubin recommended Ambrosia. We played at the Hollywood Bowl with the L.A. Philharmonic and a producer from A&M was at that show. He was impressed, he took us over to A&M for our first major-label demo. We auditioned for Herb Alpert; we weren’t signed, but we got to keep those demos. Eventually, those tapes ended up at 20th Century Fox, a new label that Russ Regan (now head of Modern Records) was heading up, and he signed us and later on we went to Warner.”

Ambrosia’s two careers in one – the early symphonic art rock and the later slickly produced pop – makes for an unusual audience, Puerta says.

“There is a real strong devoted group of fans who fell in love in that era and they still want to hear that progressive stuff,” he said. “They still call out for ‘Drink of Water’ and ‘Mama Frog,’ more early progressive stuff. They seem to accept the other side of Ambrosia, but their biggest love is the progressive stuff, so sometimes you do get a schizoid audience. By the end of the show, I think they see how we weave it together, because we do play all of it in the same show. We try to make it flow and pace it so it makes sense.”

The oldies tour is something new to Ambrosia, but they’re looking forward to the Sacramento opener, Puerta says. The show, produced by Earthtone Music, will hit several more cities in 2001, with other top-name 1970s artists expected to participate. (Earthtone also plans to launch Class of the ’80s and Class of the ’60s tour packages next year.)

THE FIRST RECORD I EVER BOUGHT: “I never had any money; we didn’t have too much money growing up, so I think I used to go into the bin at the supermarket. They used to sell weird records that you never heard of, and I think I got ‘Mule Skinner Blues’ by the Fendermen for a quarter.”

THE FIRST CONCERT I EVER WENT TO: “The Yardbirds on Catalina Island when I was 13, and Jeff Beck was the guitarist. It was a monster. And it was the first time I ever saw Fuzztone being used. It was a life-changing experience. They were such a powerful group.”

THE LAST CD I BOUGHT: “Filter’s last record, the one with ‘Take a Picture.’ It’s pretty good.”

BWF (before we forget): For nice, nice, very nice news on Ambrosia, visitwww.ambrosiaweb.com/ambrosia. … The Ambrosia album discography – “Ambrosia” (20th Century, 1975); “Somewhere I’ve Never Travelled” (1976); “Life Beyond L.A.” (Warner, 1978); “One Eighty” (1980); “Road Island” (1982); “Anthology” (1997).