On the recorded version of “Rainbow,” Riley played all the instrumentation himself, using overdubs to build layers of electric organ, harpsichord, tambourine and an Indian goblet drum called a dumbec. At Pioneer Works, the piece will be performed by younger musicians, including Angel Deradoorian, Greg Fox and Yuka C. Honda.

“Terry Riley opened a world of infinite sound in which I could submerge myself for days,” Deradoorian said. “In that realm, I felt the purest inspiration to explore the meaning of music, the power of repetition and variation on a theme, and its meditative, transcendent effects.” Fox said Riley’s music has taught him about having patience in his work: “How even small things, repeating, twirling, can be extremely familiar, and also energizing every time they reappear.”

Riley said he’s aware “people are still discovering works that I did in the 1960s,” adding that it’s “heartwarming to know that it’s still alive, that it still reaches across generations and affects people today who are living in a totally different world than when those pieces were created.”

Besides his impact on the contemporary classical world, Riley also permeated pop culture. “A Rainbow in Curved Air” inspired Pete Townshend, who named the Who’s “Baba O’Riley” (with its Rileyesque organ patterns) partly in his honor; when they met years later, Riley said, Townshend told him he owned 32 copies of the record.

He also jammed with the English prog-jazz outfit the Soft Machine and recorded “Church of Anthrax” with John Cale, which became an art-rock touchstone. Commissioned by a Philadelphia discothèque owner in 1967 to write a piece for the opening of the club, Riley taped the Harvey Averne Dozen’s soul single “You’re No Good” off the radio and transformed it into a 20-minute track that presaged the future of dance music edits and hip-hop’s sampling and looping.