Any time Ben Opie puts a group of musicians together, it promises to be a momentous event.

When he formed the avant-jazz-rock Water Shed 5tet, it had a glorious run throughout the '90s, which included his receipt of a Cultural Trust emerging artist award and Mellon Jazz Fest appearances. In convening the Opek big band and Thoth Trio, he has provided Pittsburgh with the most progressive jazz the scene has seen in years. And his Antithesis ensemble has enabled students at CAPA to enjoy the otherwise daunting task of learning New Music pieces, probably a unique experience for an American high school.

So when Opie announced he was bringing Anthony Braxton to town after months of planning and relentless pursuit of funding, it was a jaw-dropping moment that deserved as much attention as possible. There's no question that Braxton -- saxophonist, composer, writer, Wesleyan University professor, winner of the MacArthur Foundation's "genius grant" -- has been a pivotal influence in Opie's musical career.

"I've been checking out his work for a long time now, but I got much more involved in listening to it and studying it after reading 'Forces In Motion.' That's a book by [London critic] Graham Lock, an interview with Braxton and an account of his Quartet's 1985 tour of England," explains Opie. "Last year I had Antithesis mostly playing Braxton pieces, and it occurred to me that he might take on a project just because it interests him for some reason, so I suggested that he come and work with high school students."

Vocalist Eden McNutt (a co-member with Opie in the free-improv group Dust & Feathers, and the organizer of Wood Street Galleries' Radical Riffs concert series) ran with the idea to Michael Pestel, a Wesleyan instructor and former art professor at Chatham College, and a close contact to Braxton. According to Opie, what really caught Braxton's attention was the idea of playing music at the National Aviary (Pestel had been doing it for years) because it was an opportunity to do something new.

So Braxton would join the already formed Syrinx Ensemble, which included Opie, Pestel, McNutt, and double bassist Tracy Mortimore (as well as electronic musician tENTATIVELY, a cONVENIENCE for the Sunday morning edition). "We've appeared a couple times at the Central Park Zoo in New York," says Opie. "There are usually some guests stopping by, most notably [flutist] Robert Dick played with us for a little while. The ultimate success was when we got a reaction from the birds themselves."

From there, the project grew in complexity, much like a Braxton composition with its diagrams and numerals. "There was a question of how to bill it, beyond simply bringing in his group," Opie says. "After a bit of discussion, he said that he wanted to put together a large ensemble of local musicians to work with him. He tends to think big, and was also very insistent that he gets to meet as many people as he has the chance to while he's here. That's generally his attitude -- going out and finding where the local talent is."

That concept gave birth to the title of the three-day celebration -- "Braxton Plays Pittsburgh Plays Braxton" -- as well as the one-off Three Rivers Tri-Centric Ensemble, named after the Tri-Centric Foundation (established in 1994 "to stage performances of Mr. Braxton's musical multimedia and interdisciplinary works") as well as his "Tri-Axium" cultural theories about the commingling of Western art music, "trans-African" music (such as jazz and blues) and world musics. The list of Tri-Centric Ensemble members includes more than a dozen local players from such groups as Alia Musica, Capgun Quartet, Roger Humphries Quintet and, of course, Opek and Thoth.

According to Opie, there's some difficult music involved, but that's par for the course for Braxton. "It's a new music ensemble where all of the members are expected to improvise within the compositions," he explains. "There's one with a lot of writing in it, there's one that approaches more of a traditional big band piece with solos over ostinatos in the rhythm section, and then there are two pieces where there are notated sections and brief improvisations for each player, and it's all metered out. So it's a combination of fixed and open elements."

If that sounds intensive for a bunch of experienced, grown-up musicians, don't worry -- Opie isn't letting his students in Antithesis slack off, either. In the past, the youngsters have tackled the likes of Steve Reich, Terry Riley and Morton Feldman, but Opie lists two reasons he enjoys doing Braxton's works with them. "I have a lot of his scores, so there's material readily available. And finding New Music that can be played at a high school level can be tough because there's one side -- the 'new virtuosity' -- which challenges the limits of playability, like Ferneyhough, Babbit, some Elliott Carter, and early Stockhausen. So we need pieces that are within their grasp, but not by dead white European 19th-century composers."

"The thing about Braxton's work is that it covers a wide range of expression," he continues. "Last year we did an early piece of his which was a circus march, and we did another which was a wavy line that expressed levels of intensity. We've got graphic scores and complex notation and everything in between. So they're playable, with a lot of a variety and philosophical touchpoints."

As far as philosophy goes, Opie doesn't delve deeply into the Tri-Axium writings with the students, but is more interested in them mastering concepts.

"For example, when we do the Ghost Trance music, they're simple pieces where everyone reads from the same score regardless of instrument. I talk about how it's Braxton's attempt to write pieces that don't have any beginning or end. You can pick up at any point and stop at any point. We get into some unusual territory."

A clear highlight of the Braxton weekend will be a Friday night concert by his Septet -- the first avant-garde event at the Manchester Craftsmen's Guild in many years -- featuring prominent New York players such as trumpeter Taylor Ho Bynum, guitarist Mary Halvorson, and violinist Jessica Pavone. "It's similar to the Twelvetet group that played at [Manhattan jazz club] Iridium a year ago," Opie says. "Taylor and Mary were also in a recent trio of his -- the Diamond Wall Curtain Trio. I think this is a lineup that he's been developing over the past couple of years."

In addition to his compositions and theories, Braxton has long been famed for his extremely prolific recording schedule, ever since the days of his landmark 1968 solo album "For Alto," and stretching through various iterations of his Quartet, such as the '70s version with Dave Holland, Barry Altschul and Sam Rivers, or the '80s/'90s edition with Marilyn Crispell, Mark Dresser and Gerry Hemingway.

Rarely can one pick up an issue of Cadence, The Wire or Signal to Noise magazines without seeing a mention of Braxton -- this month alone, reviews appear for five separate releases spanning performances from 1979 to 2005. About such voluminous output, The Wire's Dan Warburton jokes that "Braxton ... is doing his best to hasten [the recording industry's] demise by flooding the market with more product than any sane human being can possibly hope to assimilate."

Yet Warburton's plea will go unheeded as far as Pittsburgh is concerned, which is just fine with Opie, who could very well eventually see a release on a prestigious label such as Leo.

"He and I have a recording session planned. We've talked about it a bit, and he suggested Ghost Trance duets. I'm looking over whatever scores I have and I might propose some things to him as well. Also, all the Aviary performances are being recorded and everything is being videotaped. He even talked about releasing his 'high school' CD. So I'm hoping at least one or two releases might see the light of day from this weekend."

How does Opie feel about the impending prospect of going tete-a-tete with one of his heroes? "I'm excited and a little nervous, because I've got to face down this music he's throwing at us, but I'll put myself into it with no hesitations."

And for tentative Pittsburgh audiences who might not be familiar with Braxton's vast oeuvre, what kind of assurances can Opie offer?

"First of all, take advantage of this opportunity, because this is only the second time he's even been to Pittsburgh [the first was the Ghost Trance Ensemble concert in the much-missed avant-jazz component of the Three Rivers Arts Festival back in 1998]. And go in without any specific expectations of what the music is going to sound like. Just go with it, and see what happens."