POP : When a Simple Yes Won’t Do, Mega-Group Will

They never could give a simple Yes, could they?

These days, it isn’t just Yes’s grandiose progressive rock that is complex. The band that pulls into the Pacific Amphitheatre on Tuesday is sort of a musical Siamese twin, a conglomeration of eight once and, for now, present Yes men.

The gang’s-all-here list includes four of the five founders who launched the band in 1968: singer Jon Anderson, bassist Chris Squire, drummer Bill Bruford, and keyboards player Tony Kaye. Steve Howe, the guitarist who joined in 1970, and Rick Wakeman, the keyboards virtuoso who replaced Kaye in 1971, are also on hand. Alan White, another drummer, joined Yes in 1973 after Bruford bowed out. The eighth, and junior, member of this mega-Yes is Trevor Rabin, who helped a revamped, more pop-oriented version of the band score a successful comeback in 1982 with the hit single “Owner of a Lonely Heart.”

Yes entered the ‘90s fractured in two. In one corner was the imaginatively named Anderson, Bruford, Wakeman and Howe, who actually would rather have been known simply as Yes. But the name belonged to Squire, Rabin, White and Kaye, who held onto it through some legal wrangling.

This year the two camps set aside their differences, resulting in the current ‘Yesshows ‘91’ tour. Two separate album projects were folded into a single record, “Union.”

As the tour began in March, the situation looked “almost impossible,” Howe said in a recent interview. “But your doubts pale into insignificance. From the first show onward, we knew we were doing something (Yes fans) would like.”

Howe, who just released a solo instrumental album, “Turbulence,” says that Yes will continue after the tour, although he couldn’t say precisely in what form.

Along with Pink Floyd, Genesis, Gentle Giant, King Crimson and Emerson, Lake & Palmer, Yes was one of the bands that defined the British progressive rock movement, emphasizing virtuosic playing and sweeping, classically influenced song structures. The band enjoyed its creative peak in 1971-72, releasing three strong records, “The Yes Album,” “Fragile,” and “Close to the Edge” within a span of 18 months.

A boxed set, “Yesyears,” compiling 46 tracks from 1968 to 1991, is due out the day of the band’s Pacific show.

Who: Yes.

When: Tuesday, Aug. 6, at 7:30 p.m.

Where: Pacific Amphitheatre, 100 Fair Drive, Costa Mesa.

Whereabouts: San Diego Freeway to Fairview exit, then go south.

Wherewithal: $19.25, $24.75, $27.50.

Where to Call: (714) 740-2000.