Writing dots and lines on paper is typically considered the major part of a composer’s work. But with the right collaborators and a sophisticated game plan, a composer can conjure up musical magic on an entirely spontaneous basis.

The New Jersey-born composer, conductor and multi-instrumentalist Tyshawn Sorey showed how this is done on Friday, March 25, during the enchanting final segment of the program he led and curated for the San Francisco Symphony’s SoundBox series. Under the title “Autoschediasms,” an umbrella term that Sorey uses for his particular brand of structured group improvisations, he and nine members of the Symphony unfolded a 15-minute creation boasting all the dynamism and sense of adventure that comes with treading a narrative path for the first and only time.

在他的简短的开场白的性能,the only time he addressed the audience during the two-hour program, Sorey emphasized this once-and-done quality. The version of “Autoschediasms” we were about to hear, he pointed out, would never be heard again. (A repeat performance, scheduled for Saturday, March 26, will presumably take a different shape.)

And then he was off, conducting the musicians through an unfamiliar landscape by means of a series of cryptic hand gestures. Somehow, the instrumentalists provided the notes and harmonies, Sorey provided a sturdy formal scaffolding, and together they created a rich and unforgettable musical experience.

I can’t pretend to understand the processes underlying the performance, or who exactly was making which decisions at any given time. But it was evident that, just as with a rendition of a Beethoven symphony, the bulk of the requisite labor had gone into preparation. An elaborate conceptual and structural space had been cleared to make this music possible; no one was merely winging it.

And whereas group improvisations can often devolve into a drama of vague, overgeneralized gestures — play a bunch of notes real fast, hold a low note for as long as you can — Friday’s creation was chock full of musical specifics. There were melodies in dialogue with one another, and harmonic sequences that were at once logical and full of vibrant surprises.

Perhaps the most arresting and exciting aspect of “Autoschediasms” (the title, according to Webster’s Dictionary, means“something done offhand”) was its sense of narrative drive. Just as in a fully composed score, the music moved surely but unpredictably from one leg of a journey to the next — passing through difficult terrain, cresting in a powerful climax, subsiding again — before coming to rest on a brief but poignant trombone soliloquy. The fact that this was all being summoned fresh in the moment made it feel like sorcery.

“Autoschediasms” may also have felt particularly fresh in the wake of the rest of the program, a sampler of recent music by Black composers that often tended to operate in a similar vein: slow tempos, sparse phrases, abstract rhythms.

Sorey’s “For Fred Lerdahl,” with the composer at the piano, set the tone, stringing an elegiac viola melody over terse chords for piano and vibraphone. Alvin Singleton’s duo “Greed Machine,” for vibraphone and piano, which followed it, sounded in context like a variation on the theme, and other pieces, by Tania Léon, George E. Lewis and Tyson Davis, were all given eloquent performances without quite dispelling the general air of halting tenuousness.

The exceptions were Courtney Bryan’s buoyant woodwind quintet “Blooming,” whose pointed lyricism got the evening to an inviting start, and Joseph C. Phillips’ “To Kyoto,” a chamber work with a burbling minimalist groove. They both made an eloquent case for fully notated music, even during an event at which improvisation proved to be the star attraction.

SoundBox presents Tyshawn Sorey:9 p.m. Saturday, March 26. $65. SoundBox, 300 Franklin St., S.F. 415-864-6000.www.sfsymphony.org