The Composer and the Kronos Quartet: Ideal Collaboration : Music: Apostles of Terry Riley’s music will perform at Wadsworth Theater tonight.

Minimalism gets a belated 25th birthday party Sunday when composer Terry Riley and some of the original performers re-create the premiere of “In C” in San Francisco. First performed in 1964, a planned anniversary concert of the seminal work has been postponed until now.

The performance will be without some of the greatest apostles of Riley’s work, however. The Kronos Quartet has a gig here at the Wadsworth Theater tonight, where the program includes “Good Medicine,” the finale of Riley’s monumental post-minimal “Salome Dances for Peace.”

“I was experimenting with tape loops and manipulation at the time,” Riley recalls of the origin of “In C.” “It was an attempt to do something similar with live performers, as I was also interested in jazz and improvisation.”

Any number of any kind of musicians may perform “In C,” with each running through a sequence of 53 short melodies, creating a shifting contrapuntal pattern. “I actually prefer it with combinations I haven’t heard before,” Riley says. Kronos teamed with the vocal ensemble Electric Phoenix in a local performance last year, and Riley finds the idea of an all-vocal performance alluring.

From the freedom of this countercultural icon to the formality of the tradition-rich string quartet may seem a large leap. For 15 years after the premiere of “In C,” Riley quit composing in the traditional Western sense altogether, concentrating instead on improvisation and the study of North Indian music.

But in 1979 he met the Kronos Quartet at a rehearsal while both were in residence at Mills College. From this meeting has come a stream of works for quartet, leading now even to works for symphony orchestra.

“There was a very strong feeling in me that he was a quartet composer,” says David Harrington, the Kronos first violinist, citing the beauty and intricacy of Riley’s improvisations. “He took a certain amount of convincing, however. When we first began talking about a quartet, he had not written down any music since ‘In C.’ ”

Riley, for his part, has found Kronos an ideal collaborator, open to new challenges. “They’re not only willing, I think they cry out for it,” the composer says. “They want to grow and create a much wider repertory. Fortunately, the string quartet is a very adaptable medium.”

In the case of “Salome Dances for Peace,” recently released in a Kronos recording on Elektra Nonesuch, the medium has been stretched to encompass a two-hour marathon in which the biblical temptress Salome searches for peace in a landscape of Third-World myth.

“The kind of writing, the integration of the parts, takes a lot of concentration,” Riley acknowledges. “Just the length alone is very demanding.”

Harrington agrees. “I figure it took us, on and off, three years to learn to play. The rhythmic considerations are enormous, as well as the interpretive dilemmas because he has deliberately chosen not to edit his music, but to leave many performance decisions to the players.”

Riley and Harrington also agree that minimalism is not the word for this music. “The importance of the beat and pulse is there,” the violinist says, “but at this moment Terry is bringing his world together in a very large way and not fracturing it into small events.”

Minimalism, Riley says, is “not an apt description of the work that I’ve done, but it’s probably going to last for a long time. Where it falls short is that it seems an intellectual term and doesn’t suggest the ecstasies of the music.”

At the Paris premiere of “Salome,” there was only what is now Part I. From there it grew, something Riley pieces tend to do. “There are really five quartets here, bonded together by the style and the world view,” says Harrington.

Riley ruefully acknowledges this proclivity for unplanned growth in his music. His first symphonic piece is “The Jade Palace Orchestral Dances,” commissioned by the St. Louis Symphony for performance in the Carnegie Hall centennial celebrations. “Like all my pieces, it’s turned out to be more than expected. I was supposed to write 15 minutes, and it’s now 55 minutes!”

The 54-year-old composer lives and works in the Sierra Nevada, where he was born, with his wife and two children. Composing--including a piece for orchestra and Kronos commissioned by the Salzburg Festival--and touring keep him busy.

Riley originally intended “Salome” to be a ballet, though there are no definite plans to dance the work at this time. “We’d love to do it at the United Nations on very special occasions,” Harrington says. “There is a plan I would hope to be able to announce soon.”

The rest of the Kronos program Saturday includes the world premieres of “Monody” by Jose Evangelista and “Doom (Sigh)” by Istvan Marta, Philip Glass’ Quartet No. 4, and a set of pop arrangements. “In this case,” says Harrington, “we’re putting together the strongest works we know at this time.”