They’re All 4 Doing Live Shows : Jazz: Fourplay has had a No. 1 for six months but had never gone on tour. This weekend it will be, in San Juan Capistrano and other Southland cities.

Fourplay may not be a name that resonates with instant recognition, but this all-star jazz group has to be one of the musical success stories of the year. Its debut album has had a lock on the No. 1 position on Billboard’s contemporary jazz chart for the past six months.

Amazingly, until last week, Fourplay had done it without a tour or TV guest spots and with minimal publicity. But beginning Saturday at the Pantages, the group--which includes Bob James (keyboards), Lee Ritenour (guitar), Harvey Mason (drums) and Nathan East (bass)--will make its initial and probably only Southland appearances of the year as part of a 2 1/2-week tour. There are also dates Sunday at the Coach House in San Juan Capistrano,

Monday at the Ventura Theatre in Ventura and Friday atthe Spreckels Theatre in San Diego.

“It hasn’t been easy, getting us all together in the same place, because we all have very busy individual careers,” Mason said.

Although they had worked together in various combinations for years, the four players never gathered as an ensemble until they recorded James’ 1990 album, “Grand Piano Canyon.”

“For a long time before that,” said James, “I’d had a fantasy of what it would be like to be a member of a cooperative group. I’ve never really been in one, but I’ve watched democratic bands like the Modern Jazz Quartet or the Yellowjackets, where there was an identity that the group had that was different from that of the individual people.

“Coincidentally, when we were doing the ‘Grand Piano Canyon’ album, we just had a great time in the studio. Well, I looked around, and there we were--four people who all seemed to feel the same way about music, who had the same enthusiasm for the same thing. So I thought we might as well talk about the idea of a group, not really thinking they would go along with it. But they did.”

The timing was perfect. James had just begun to do talent scouting for Warner Bros. He took the idea to the company, which signed the group.

The band’s achievements have been an unexpected bonus. At the most, they saw Fourplay as a pleasant adjunct to their own individual careers. The real value was the opportunity to work together.

“That’s really all we were thinking when we made the album,” Ritenour said. “There’s a very subtle musical weave in this group, and it’s one that makes it very appealing as a musical environment.

“I think, in part, it’s because we all think about music in very similar ways. We’re all strong rhythm players. At the same time, we all write songs, and we’re all very melody-oriented. And, finally, none of us are really very busy players--in terms of playing flurries of notes. And that’s something unusual. I don’t think I’ve ever been with a band where there was such a respect for balancing the sounds and the silences, for letting the music breathe.”

Some of the critical reaction to Fourplay, however, has not been quite as enthusiastic. Several reviewers have dismissed the music as lightweight. Others would prefer a more mainstream style from this particular combination of jazzmen.

‘I’m not so sure that they get the point,” Ritenour said. “On the surface, some of our music may sound similar to other contemporary groups, but when you get inside, there’s much more happening.”

James agreed and also questioned some critics’ perspective: “If someone understands the genre and doesn’t think we’re cutting it within that genre, then I can accept that as a valid criticism, but I have problems with (negative) reviews by someone who just isn’t into the genre.”

“The funny thing is,” Ritenour said, “that when Bob said that he wanted Fourplay to be a kind of contemporary version of the Modern Jazz Quartet, one of the reviewers said, ‘Dream on.’ Well, we’ve been on the charts for six months now, so maybe that’s what we’ll name the next album--’Dream On.’ ”

Fourplay will perform Sunday at 7 and 9:30 p.m. at the Coach House, 33157 Camino Capistrano, San Juan Capistrano. $23.50. (714) 496-8930.