George Lewis is one of the most formidable figures in modern music: a composer of international renown, a legendary improvising trombonist, a computer-music pioneer, a professor at Columbia, a stalwart of the Black avant-garde collective known as the Association for the Advancement of Creative Musicians. Yet a routine encomium to Lewis’s achievements and influence would ignore the import of his scholarly writings, which resist the usual narratives of individual genius. His 2008 book, “A Power Stronger Than Itself: The AACM and American Experimental Music,” is a riveting portrait of communal originality, with the author assuming a background role. Let’s simply say, then, that this genially authoritative figure deserves an extended round of applause. At the age of seventy-one, he is at the height of his productivity; he had seven premières in 2023, in New York, Vienna, and points in between. In a December concert at the Park Avenue Armory, the International Contemporary Ensemble, of which Lewis is the artistic director, played his music on a double bill with a performance by the composer-pianist Amina Claudine Myers, another A.A.C.M. veteran. The ensemble has also recorded “Afterword,” Lewis’s first opera. His second, “Comet/Poppea,” arrives in June, in Los Angeles.

Lewis grew up in Chicago, the son of Southerners who had come North as part of the Great Migration. As a third grader at the University of Chicago Laboratory Schools, he took up the trombone, which, he later wrote, appealed to him as “big, shiny, and weird.” He went on to Yale, where he studied music theory and majored in philosophy. On a break from college, he joined the A.A.C.M., which had formed on the South Side of Chicago in 1965, with Muhal Richard Abrams, Anthony Braxton, Joseph Jarman, Roscoe Mitchell, Wadada Leo Smith, and Henry Threadgill among its early members. Their music combined African American traditions with insights gleaned from classical modernism and various world cultures. The A.A.C.M. tended to be categorized as avant-garde jazz, although, as Lewis’s scholarship has shown, it should have been incorporated into a canon of experimental composition that has a long history of shutting out Black artists.

The trombone was the vehicle of Lewis’s initial breakthrough. His astonishing technique ran the gamut from delicate filigree to unearthly howling. In 1977, Whitney Balliett, this magazine’s longtime jazz critic, reported that at one A.A.C.M. event Lewis had unleashed “four consecutive—almost overlapping—ascending arpeggios played in sixty-fourth notes and in different keys,” and that a little later he had “mumbled funny gibberish through his instrument.” The A.A.C.M.’s experimentalism often had a streak of the carnivalesque. Myers, in her set at the Armory, maintained that tradition with an uproarious piece titled “Stay in the Light,” in which she and her collaborators—the bassist Jerome Harris, the drummer Reggie Nicholson, and the vocalist and dramatist Richarda Abrams—enacted a mini-opera at once satirizing and celebrating the search for spiritual enlightenment.

In 1982, Lewis moved to Paris to work at ircam, Pierre Boulez’s lavishly funded electronic-music studio. Defying a prevalent high-modernist mentality, Lewis programmed Apple computers to react to live sonic input and deliver improvisatory responses. (“Rainbow Family,” his major project at ircam, can be heard on Carrier Records; the saxophonist Steve Lacy, the multi-instrumentalist Douglas Ewart, the guitarist Derek Bailey, and the bassist Joëlle Léandre took part.) Lewis later introduced an interactive human-and-machine software platform called Voyager. He has therefore had long experience contemplating the philosophical issues around artificial intelligence. His conclusion is that the behavior of the machine depends heavily on who is programming it. In an essay about Voyager, he argues that his system enacts the density and multiplicity that have long characterized Afro-diasporic music-making.

In the nineties, Lewis took up his first major academic post, at the University of California, San Diego. He soon gathered admirers in the contemporary-classical field, not least because of the force of his intellect. So many heady ideas proliferate in his pieces—titles such as “Tractatus,” “Mnemosis,” and “Signifying Riffs” give the flavor—that one can overlook their visceral appeal. Granted, Lewis is by no means an easy-listening composer: his episodes of controlled chaos can rival the stormiest creations of the European avant-garde. But his acute ear for instrumental timbre means that the textures never devolve into murk. One signature device is to pit shrill, birdlike cries in the upper winds against sustained, heaving sonorities in the bass. You hear this oceanic, almost Wagnerian effect in Lewis’s large-scale orchestral work “Minds in Flux,” which had its première at the Proms, in London, in 2021. (American orchestras should take it up.) At the same time, he hasn’t lost the impish wit of his youthful outings.

The two scores that Lewis presented at the Armory embodied a dialectic of complexity and play. First, the International Contemporary Ensemble, under the direction of Rebekah Heller, lit into the 2013 piece “Assemblage,” whose title alludes both to Deleuze and Guattari’s concept of agencement—“contingency, heterogeneity, nonlinearity, and emergence,” in Lewis’s paraphrase—and to the artistic practice of reworking junk objects. At the beginning, eruptive full-ensemble gestures give way to a gently purring harp figure and to snappy rhythms on agogô bells. These incipient grooves are almost immediately waylaid by fresh alarms and excursions. The ensemble had no trouble adopting Lewis’s turn-on-a-dime energy, conveying a kind of happy exhaustion at the end.

“Blombos Workshop,” for solo piano, written in 2020, is inspired by a seventy-three-thousand-year-old abstract design found in the Blombos Cave, in South Africa. The piece seems to conjure a prehistoric avant-garde musical workshop, a sonic analogue of the visual culture that can be glimpsed in the cave. Fully notated passages—scampering runs, precisely hammering chords, ghostly arpeggios—are interspersed with opportunities for improvisation. The first twenty-four bars indicate rhythms, dynamics, and registers but not precise pitches. The ending, too, is left open. Cory Smythe, himself a composer and improviser of note, proved an ideal conduit, making the distinction between Lewis’s ideas and his own elaborations inconsequential.

“Afterword,” which had its première in 2015, is in some ways Lewis’s most conventional score to date. It is an opera in eleven scenes, fully notated. The libretto, however, is thoroughly unorthodox. It tells the story of the formation of the A.A.C.M., mining material that Lewis gathered for “A Power Stronger Than Itself.” The composer has, in other words, made an operatic adaptation of the scholarly history that he wrote about the collective to which he belongs. We’ve come a long way from the Florentine Camerata—yet not immeasurably far, since several founders of the opera genre mythologized themselves as Orpheus, the original composer. In “Afterword,” new myths are afoot. The libretto tends not to specify individuals, instead assembling a collage of overlapping voices. As in the book, the focus is on the collective workings of a community. “Heroes, gods, and masters do not exist in our sight” is one crucial line.

The opera’s musical idiom has its own contrarian magic. Lewis adopts a fairly severe non-tonal language, with angular vocal lines piercing thickets of dissonance. Some listeners have found the result disconcerting: people raised on the South Side seem to have been possessed by the spirit of Arnold Schoenberg. To my ears, it’s a productive defamiliarization effect, banishing stereotypes and signalling cross-cultural influences. (Threadgill, in his recent memoir, “Easily Slip Into Another World,” written with Brent Hayes Edwards, recounts being dumbstruck by his first encounter with Schoenberg’s “Pierrot Lunaire.”) There’s also an arcane comedy at work. In a scene depicting the A.A.C.M.’s inaugural meeting, which included a strenuous debate about the nature of originality, one voice sings, “Do people even know what original music is? I don’t.” In response, we hear the instrumental equivalent of a wry smile: low cello tremolo, some light taps on cymbals and tam-tam, a quizzical piano arpeggio. Let’s start with that. ♦