To call John Adams's "El Nino" exactly what it is--an oratorio on Christ's nativity, supplementing the New Testament account with Spanish poems by women poets--may give you the wrong idea. Is this some trite attempt to subvert the Santa Clausian sublimity of Handel's "Messiah" with perverse postmodernism? (Adams, after all, is the guy whose 1987 opera "Nixon in China" gave Tricky Dick an aria about hamburgers.) Or to replace a patriarchal, English-only narrative with a more "inclusive," "woman-centered" text? Well... wrong. Just about no one who's heard "El Nino" has been able to resist its house-rocking rhythms and its rich variety of melodies and textures: from the astringent medieval harmonies of a trio of countertenors to the lush, operatic outpourings of its two Marys, the silver-toned lyric soprano Dawn Upshaw and the golden-toned mezzo Lorraine Hunt Lieberson, to a heaven-shaking adult chorus and an achingly gentle chorus of children. It's probably too soon, but we might as well say it: this was a great rendering of a great work by a great composer.

In fact, even to call "El Nino" an oratorio is misleading. That's what it'll be when a CD version comes out, but last week's North American premiere with the San Francisco Symphony was a sort of multimedia opera, directed by Peter Sellars, who did "Nixon in China" and Adams's even more controversial 1991 opera, "The Death of Klinghoffer." The principal singers, Upshaw, Lieberson and the titanic bass-baritone Willard White (both Joseph and Herod), move in elaborately choreographed dramatic gestures and are shadowed by a trio of dancers; high above the onstage orchestra and chorus, a silent film by Sellars--shot in both digital video and wonderfully funky Super-8--tells a parallel story, with the same dancers and a teenage mother in East L.A. All this visual information makes it impossible to give Adams's music your full attention. Conductor Kent Nagano, another longtime Adams collaborator, recognizes that this overload was Sellars's intention, but as a musician he can't help adding that he's always been "a firm believer in opera being performed in concert. First and foremost, it's a musical form." Sellars has a different agenda. "I'm not interested in opera per se," he says. "What I'm interested in is collaboration. It's like those medieval churches, where there's way too much going on. Mary's giving birth here, she's dying there, she's received into heaven there. That sense of simultaneity, that there's always something more than you can grasp--I love that."

But Nagano and Sellars agree that "El Nino" is a major breakthrough for Adams. Nagano calls it "if not the greatest, certainly one of his greatest accomplishments. It's very much a development of John's musical language." (The piece seamlessly integrates Adams's trademark touches: the hypnotic repetitions of short phrases and the harmonic simplicity of his early minimalism, the complex melodies of his later romanticism and the spiky modernism of his work in the early '90s.) Sellars believes that for the first time Adams has become "a true vocal composer. He's previously been an instrumental composer who puts vocal lines in his music." Adams laughs when this is repeated to him. "Well, of course they'll say that," he says. "Every piece is a 'breakthrough'." He laughs again, then he proceeds to agree, sort of, with both of them. "I don't want to typecast myself, and I may regret saying this, but I have a feeling that I've been going through a synthesis of all that I've done. The 'major breakthrough' in this piece is just writing naturally for voice."

But something more radical has happened to Adams: he's become, without having intended it, a sacred composer. "I don't think the word 'sacred' ever came into my mind when I was writing 'El Nino'," he says. "And now I suddenly find myself in interviews having to answer a lot of alarmingly personal questions about my beliefs. I'm not a practicing religious person, and I didn't have any sound bites ready. But now I'm interested in continuing to work with this mythology. In rereading the New Testament, I've been stunned by all the miracles there. They make anyone who's even remotely logical profoundly uncomfortable." And miraculous discomfort, needless to say, is just what any artist who's even remotely logical will go toward. So what's next? A Passion? An Easter oratorio? Well, not without some time to regroup. "Right now," Adams says, "I just want to write a simple piano piece."