When Alan Silva brings his Celestrial Communication Orchestra to Emmanuel Church this Friday, it will be one of the great conclaves of the current avant-garde scene. The CCO will bring together brass players Roy Campbell, Joe McPhee, Steve Swell, Joseph Bowie, Joe Daley, Bill Lowe, and Itaru Oki, a reed section of Marshall Allen, Kidd Jordan, Jemeel Moondoc, Sabir Mateen, Perry Robinson, and David Sewelson, guitarist Joe Morris, bassist William Parker, percussionists Jackson Krall and Laurence Cook, and vocalist Leena Conquest. Silva will conduct and play synthesizer.

Silva is one of the founding members of the ’60s free-jazz movement, having played with Cecil Taylor, Albert Ayler, and Sun Ra, as well as Archie Shepp, Sunny Murray and others, and it’s a testament to the respect he’s earned over his career that he can gather a group like this in one place at one time. You’d be hard-pressed to name a recent occasion when Allen, the still-vital 78-year-old alto-sax patriarch of the Sun Ra Arkestra, shared the stage with 64-year-old clarinettist Robinson.

Although schooled in several instruments, including cello and trumpet, Silva, who is himself 64, made his name as a bassist who was capable of swinging from his heels with an all-out percussive attack, or wending his way through long-form free-jazz pieces like Taylor’s "With (Exit)" (from 1966’s Conquistador!) with delicate, skittering filigree played with the bow. He has lived mostly in France since 1972, where he formed his first large orchestra with mainstays like pianist Bobby Few and saxophonist Frank Wright and at various times the likes of Shepp, Anthony Braxton, and Leroy Jenkins. Silva has always preferred synthesizer while working with his large bands, since it’s better suited to his method of "conduction."

Conduction is a method of spontaneous composition (on the bandstand, as it were), a means of directing large forces in collective improvisation. On Silva’s recent recordings, you can hear the all-out skronk of 22 musicians going at it with complete freedom, having nothing to guide them but their ears and Silva’s directions. Yet free as Silva’s pieces are, they do have shape and texture — places for solos, for sectional interplay. Occasionally he’ll set a harmonic framework with two rocking chords on his keyboard, or the rhythm section will play a very loose, swinging 4/4, or he’ll send a long brass melody line over the top of agitated reeds (there are signs that some of these figures are worked out in rehearsals, whether written or not). Silva cues with hand signals, synth figures, or shouted phrases that the band repeat with their instruments. The results can be alternately exhilarating and frustrating. On Alan Silva & the Sound Visions Orchestra (Eremite, recorded in 1999 in New York City), there are wonderful pianissimo sections for muted trumpets, bassoon, timpani, and French horn as well as vivacious reed-section screamfests.

Talking over the phone from Northampton, Silva cites influences as disparate as Ornette Coleman’s Free Jazz, John Coltrane’s Ascension, the work of Duke Ellington, Sun Ra, and Charles Ives, and, in the use of electronics, that of composer George Russell and theorist Joseph Schillinger, with a nod to Russell also for the "vertical forms" of his Lydian Chromatic Concept. The goal, he says, is "to "improvise in real time an entire orchestra piece." Which is one reason not to miss his work live.

Alan Silva and the Celestrial Communication Orchestra play at Smith College’s Helen Hills Chapel, on Elm Street in Northampton, tonight, February 27, at 8 p.m. (call 800-999-UMAS), and at Emmanuel Church, 15 Newbury Street, tomorrow, February 28, at 8 p.m. (call 617-927-6605).

THE TRIO who call themselves Fieldwork is after a different kind of freedom. On their Your Life Flashes (Pi), they move in and out of boppish chord progressions, but they’re most noteworthy for their constant manipulation of odd meters at high velocity. There are all manner of sixes, sevens, and fives here; there’s even "free" time (if they did a straight 4/4, I missed it). If this sounds cool and intellectual, it’s not — the tempos and drummer Elliot Humberto Kavee’s relentless cross-rhythms maintain a propulsive groove, and there’s a strong pulse even on the relatively free-form "Accumulated Gestures." At times the flavor of the band, with its repetitive, morphing riffs, is closer to rock than jazz. Pianist Vijay Iyer is happy to spend a lot of time comping in sharp metric chords against Kavee and saxophonist Aaron Stewart, but he also employs dense Cecil Taylor clusters and fractured Paul Bley single-note lines. The band pack 10 pithy tunes into 50 minutes — another jazz anomaly. You can check out pianist Iyer in the duo Raw Materials with saxophonist Rudresh Mahanthappa at the Isabella Stewart Gardner Museum, 280 the Fenway, this Saturday, March 1, at 1:30 p.m.; call (617) 566-1401.