Yes and Yes Again : With two new albums in a month, and a tour, the decades-old group seems very much alive.

What would you think of a rock ‘n’ roll band that releases two full-length albums of brand new material within the same month, one with catchy, commercial pop songs, and the other with majestic, musically articulate 10-minute suites?

One would assume that a band responsible for such an eccentric and ambitious endeavor would be young, and probably from England--a bunch of newcomers to the scene, hungry to prove that their musical imagination knows no limits.

But this band (its members are, indeed, British) has been together for almost 30 years.

It’s Yes, the most trendy of art-rock groups of the mid-’70s, and, in these times of post-grunge, pop-punk, girl-power madness, the musical equivalent of a harmless, leaf-eating brontosaurus.

The band is hardly worried. For the first time in more than a decade, it has the goods to prove it has bite.

In a telephone interview from Tulsa, lead singer Jon Anderson talked about the current Yes tour, which includes a stop at the Universal Amphitheatre on Sunday.

“We’re very excited to be back on the road after a standstill of three years,” he said enthusiastically. “This is the classic Yes lineup, and the show is getting better and better.”

It was in the early ‘70s that Yes, a group formed in London out of a casual meeting between Anderson and bassist Chris Squire, started to experiment with a different approach to pop craftsmanship.

“The audiences were quite different back then,” explained Anderson in a previous interview, conducted in 1994. “You could play long songs, you could mix classical music with jazz and folk. Today, if you don’t have a three-minute instant radio hit, you’re done for.”

That era’s open-minded attitude allowed the classic lineup of Yes (Anderson, Squire, Steve Howe, drummers Bill Bruford and Alan White and classically trained pianist Rick Wakeman) to follow the path of artistic experimentation, a choice that unexpectedly turned commercially viable.

Under the Yes treatment, pop music became a flexible kind of thing, something you could stretch in any direction you wanted. Melody wasn’t the central focus anymore, or at least it had equal footing with rhythm, timbre, mood and texture. If Yes had been a classical composer, you would think of a Russian, a la Prokofiev or Shostakovich, but infatuated with French Impressionists such as Ravel or Debussy.

This attitude peaked on a double record set titled “Tales From Topographic Oceans,” which stretched its sonic canvas to four 20-minute songs dealing with metaphysical concepts. To some, it was a musical epiphany. To others, it was a nadir, everything rock ‘n’ roll was not supposed to be. “We wanted to push the musical experience as much as we could,” said Anderson, who ranks “Topographic” as one of his favorite Yes albums.

Officially, the band is now promoting “Open Your Eyes,” its new album on Beyond Music that was just released. The record is a collection of tunes that recall the 1983 best-selling “90125” and its smash hit “Owner of a Lonely Heart.” The new album’s first single has been getting some attention on radio play lists.

But three weeks earlier, Cleopatra Records launched another Yes opus, this one a double CD called “Keys to Ascension II.” It includes a disc of live material recorded last year, plus almost an hour of new music.

Whereas the pop songs in the “Eyes” album are sprinkled with Howe’s refined guitar work and sport the band’s trademark, epic three-part vocal harmonies, these nuggets are nothing compared to the scope of the “Keys” studio tracks, one of which, at almost 20 minutes, definitely recalls the sheer magic of the “Topographic” records.

According to Anderson, the simultaneous release of two new albums is almost coincidental. “When the old Yes lineup got back together in 1995, there was a very conscious effort to create something special. And the music in ‘Keys to Ascension I’ (released in 1996) and ‘II’ reflects what happens when those people make music together.”

“But while we were waiting for Rick [Wakeman] to make up his mind about touring, Chris and [new member] Billy Sherwood started composing some songs. Soon enough, I joined them. It was just something to do, because we had spare time. Eventually, the songs were put together as a record, but it was a very different energy source from the “Keys” project.”

If the live disc from “Keys” is any indication, the show at Universal should be a lavish, stunning affair. Yes has revisited old favorites such as “Close to the Edge” and “Time and a Word” with a freshness that was unheard of in previous tours. Although Wakeman can be heard on these recordings, he is absent from the tour.

“It is difficult to understand,” said Anderson, “but Rick wanted to be part of the band, and not tour. And we waited and waited for him to make up his mind, until he finally said no.”

His replacement is Igor “Ivan” Khoroshev, a Russian pianist who knew all of Yes’ records by heart before he joined the band. “‘He’s really talented,” said the singer. “I’m really looking forward to composing new songs with him.”

The Yes lineup is also augmented by Sherwood on guitar and backing vocals. But search as you may, you will not find Trevor Rabin on the stage. The South African guitarist responsible for the Yes renaissance that took place in the ‘80s is no longer part of the band.

Rabin, together with producer Trevor Horn, was the man responsible for updating Yes for ‘80s radio listeners, and giving the group its first No. 1 hit, with the syncopated metal-pop of “Owner of a Lonely Heart.” But the band was stuck trying to repeat the huge success of that single, and by 1994 the over-produced “Talk” album failed at the charts, and Yes was left without a record company.

Rabin jumped ship and is now busy as a successful composer for Hollywood soundtracks.

The other Yes members, who have played together since they were in their 20s, had really nowhere to go. Thus, they stuck together and continued writing and recording songs. “We haven’t talked about retiring yet,” said Anderson, still youthful and recently married at 53.

“We’ll tour for the next two years, record an album for the 21st century, and then see what happens.”

BE THERE

Yes performs at 8:15 p.m. Sunday at Universal Amphitheatre, 100 Universal City Plaza. Tickets range from $25-$55. Box office number is (818) 777-3931. Ticketmaster number is (213) 480-3232.