Hair returned to its roots last summer in a revival production mounted by The Public Theater at Central Park's Delacorte Theater. Cracks of thunder and bolts of lightning accompanied the opening all night long, but it was not till the closing moments of the show, when the hippie commune onstage uttered the words, "Let the Sunshine In," that the rains came. They came in buckets, drenching actors and audience alike.

Somehow, the cast finished the show and took their bows when the audience suddenly charged the stage and joined them in their wet revelry. There's something very freeing in the spectacle of Oskar Eustis, hirsute head of The Public, dancing up his own storm in the hammering downpour.

"It was quite uncanny," concedes the show's composer, Galt MacDermot, 80. "It certainly felt like an omen of some kind, and it turned out to be a pretty good omen."

James Rado, 76, another of the triumvirate who created this landmark musical, agrees: "That's what I call supernatural. I suspect Gerry might have been behind the rain effect at the end of the show. He would really have loved this production." "Gerry" was Gerome Ragni, the charismatic sparkplug of the show who died of cancer in 1991 at age 55. He and Rado spent two years crafting the lyrics and book to Hair: The American Tribal Love-Rock Musical, then entrusted their labors to MacDermot, who knocked out one of the great Broadway scores in three weeks. The show first saw life Off-Broadway in October of 1967, opening The Public Theater's downtown home — the first non-Shakespearean offering Joseph Papp had done. Come April, it became the first musical to move from Off-Broadway to Broadway.

Rado and Ragni met in 1964 at an Off-Broadway cattle call for an opus portentously titled Hang Down Your Head and Die. "We liked each other right away," remembers Rado, "and the next day, we got news that we both had been cast. We had a number of previews, and then it had an opening night — and closed. One performance only."

But the friendship was for the ages — and the arts: Eventually, they came to the conclusion that there was a musical to be found in the turbulent times in which they lived — specifically, the war-protesting hippie counterculture and sexual revolution of the '60s — and their plot was a transplant of La Bohème to those times. When they saw two men strip naked at an anti-war demonstration in Central Park — as an act of defiance and an expression of freedom — they decided that had to be in the show. "We became totally enamored with what was going on. The love element of the peace movement was palpable. You could really feel it, really experience it."

Lording over their youthful agitations were veiled facsimiles of themselves. Indeed, Ragni originated the role of Berger the firebrand Off-Broadway, and Rado joined him on Broadway as Claude, a draft-dodger as undecided as Hamlet about what to do.

"Claude is more introspective and sensitive," says Rado. "I was shyer than Gerry. Gerry was gregarious — a life force — and I was attracted to that, as many people were. He had this element of the wild guy in him and could look wild because his hair was so huge. We didn't even know that when we wrote the show. He just had a good head of hair, but it was short. In the sense of male connectedness, which happened in the hippie movement and which happened between Gerry and myself, it's autobiographical."

MacDermot wasn't the first choice for composer. A Canadian married-with-children and relatively square in the ways of the world, MacDermot hardly seemed the right match for Rado and Ragni — but was, he says: "I never even heard of a hippie when I met them. What I got on to was the music of the times. I had just moved back from South Africa, so I was very into African music, and the rock 'n' roll that was happening in the '60s was that, so when they said, 'We want to do a rock 'n' roll show,' I said to them, 'That's exactly what I want to do.'

"When you say you want a rock 'n' roll show, you're talking about two hours of music. It can't all be the same. You've got to get different styles. I never counted them, but I like to think they're all a little different. 'Aquarius' has a bit of a West India feel. I was trying to make it spacey — like outer-spacey — and got too spacey. Jim said, 'The kids'll never sing a song like that.' I agreed. It was the only song I rewrote.

"Gerry loved making everything into a song. 'What a Piece of Work Is Man' was not a song until Gerry said, 'We have to sing that.' 'Frank Mills' wasn't a song. That began as a speech, and Gerry said no. He loved songs. He'd have turned it all into a song."

Coming all at once — the profanity, the promiscuous use of drugs and sex, the irreverence for the American flag, the nudity — Hair was, and is, unlike any other Broadway musical. "I'm proudest of the fact that we captured what was happening at that time," says Rado. "It was very important historically, and if we hadn't written it, there'd not be any examples. You could read about it and see film clips, but you'd never experience it. We thought, 'This is happening in the streets,' and we wanted to bring it to the stage. When you were there in person, it had such impact."

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The Public Theater production of Hair, directed by Diane Paulus, is at Broadway's Al Hirschfeld Theatre.