It was the evening of March 14, 1956, and "My Fair Lady" was having its last preview before the critics delivered their judgments at the official opening, to occur the next night. Fretful, Alan Jay Lerner, the playwright and lyricist, paced back and forth all evening in the rear of the Mark Hellinger Theater, simultaneously monitoring the show and the audience.

"After the final curtain fell, I went backstage, and, as usual, made my first stop in Rex's (Harrison) dressing room," he writes in a new book, "The Street Where I Live." "It was crowded with enthusiastic friends, among them the well-known producer, Leland Hayward, and his wife Nancy, more familiarly known as 'Slim.' Despite the success of the evening, it was still not the opening and my furrowed brow must have revealed my inner anxiety. Slim took one look at me, and dragged me outside Rex's dressing room.

"'Alan,' she said sternly. 'Listen to me and listen to me well. What is happening in this theater is incredible. It is something that has happened to few people and will never happen to you again. So, for Christ's sake, stop worrying and enjoy it. Do you hear me? Enjoy it!'"

It was sage advice to a shaky 37-year-old who still couldn't quite believe that he, composer Frederick Loewe and director Moss Hart had shaped a masterpriece of the lyric stage out of Bernard Shaw's play "Pygmalion." Twenty-four hours after the opening, there could be little doubt.

His record of success both on the stage and in the movies is unexcelled by any living playwright-lyricist: "My Fair Lady" won the New York Drama Critics Award, the Antoinette Perry Award, and so on; "An American in Paris" got an Oscar for the best screenplay; "Gigi" cornered an Oscar for best movie. He also wrote "Coco" with Andre Previn and "Love Life" with Kurt Weill.

The Lerner of today is a slight, dapper man who talks in precise, graceful sentences, smoking an occasional cigarette, generally with an apology and a pledge that he will give up smoking. He is a model of courtesy, holding doors for his guest, and answering the phone himself even when it turns out usually to be for his guest.

Now 60, Lerner carries on at the same pace of composition that he has maintained since he and Loewe first collaborated in a stock company in Detroit in 1942. "My pace is about one show every two years. Though I'm running behind on the latest one, tentatively called, 'Carmelita,' which is scheduled to open at the Kennedy Center on March 6." The composer is Burton Lane, with whom Lerner wrote "On a Clear Day You Can See Forever."

Why, then, with all these time presures has Lerner taken the time out to take stock and write a spicy, stylish and sometimes almost elegiac memoir of his relationships with his principal mentors and collaborators?

"Quite frankly I miss Fritz (Loewe) and Moss," says Lerner, "and I wanted to get my memories down on paper." Hart died in 1961, not long after the three of them collaborated for the last time in "Camelot." And Loewe retired to Palm Springs.

But perhaps the man about whom Lerner writes with the greatest compassion is his father, the wealthy founder of the Lerner department store chain. Of three sons, he says, "I was my father's favorite and I adored him."

His parents were separated, but his father hardly neglected him. "He loved the musical theater and from the time I was 5 years old there was hardly a musical on Broadway that he did not take me to see. By the time I was 12 I had only one ambition and that was to be involved, someday, somehow, in the musical theater."

Lerner points out two other traits of his father that were to shape Lerner's own work. One was an obsession with words and syntax. "Even after we had won a Drama Critics' award for 'Brigadoon,' he said to me one weekend, 'Alan, I have counted the words you have used this weekend and you have an active vocabulary of 297 words. I do not see how you can make a career as a writer that way".

Then Lerner describes his father's rigid adherence to what he regarded as maturity, "to go through life in a permanent state of self-protection" and his lack of respect for anything but the physical properties of women. Comments Lerner: "The heart may have its reasons of which the reason knows nothing; but reason all too often has no heart."

This is, in effect, the central theme of "My Fair Lady." And most of these traits are principal ones of its central character, Henry Higgins.

It was Lerner who kept pushing the "Pygmalion" musical poject when others were ready to give up.

And Lerner acknowledges subiliminal link between Higgins and his father. "Something touched me. And certainly Higgins touched me more than Eliza Doolittle. Higgins was a lonely man and my father was a lonely man. And both were carried away with words and both of them thought females to be inferior.

"And, for that matter, the same was true of Shaw. When Shaw was writing satire, he's practically the only such artist I've read who was not bitter. You just have to read his letters to see that there was a romantic under all that. For all that, there was one major difference between Higgins, Shaw and my father, and that was Shaw's celibacy," a point amply documented in Lerner's book. Lerner senior was very much a womanizer.

"My Fair Lady" was the fifth of the Lerner and Lowe musicials.

It was a fluke that Lerner was to become famous in partnership with a man 17 years his senior. Normally a member of Harvard '40 who would have been fighting in World War II. But while sparring one day on the Harvard boxing team, "My mind wandered, my guard dropped and a left hook to the side of the head removed all sense from my expression." Eventually, he lost all vision in one eye.

But for that misfortune he would never have met Loewe. And Lerner acknowledges that even as late as "My Fair Lady" "Fritz was the only one who really knew what was happening, and wasn't nervous about the show. It was a difference in culture. He was imbued with a sense of it as he grew up in Europe, and he could stand back and look at something we had created and see it dispassionately. That's just something I'll never have.

"I still keep in close contact with him by phone, and I guess one of the reasons I wrote the book is that I hoped that reading it would make him happy."

Lerner acknowledges two traits that made him particularly suitable for the big musicals of the '40s and the '50s. One is that he is a "romantic at heart" and the second is that he writes lyrics that are about "character" and advance the story. "Satire, and other forms, are just not for me.

"For instance, Lenny (Bernstein) offered me 'West Side Story,' but I decided not to. That kind of tense drama was done much better by (Stephen) Sondheim and (Arthur) Laurents. Considering the role of the dance, "West-Side Story" ended up the best show integrating all the elements of the musical since "Oklahoma."

Of "1600 Pennsylvania Avenue," the only Bernstein-Lerner collaboration, Bernstein said in a recent interview that he feels the show could have been salvaged and saved its ignominous closure before it formally opened.

Lerner is more dubious. "I agree that the show was sprinkled with moments that Lenny and I could be proud of. But there was a fatal flaw, because stylistically Lenny and I were writing two different shows. I try to write emotion not so much by confrontation as by tenderness. I'm not sure that my natural way of writing can be dramatized that forcefully."

Lerner's new show is for the Kennedy Center's Roger Stevens, as was "1600." "I'll never forget the generous farewell party he (Stevens) threw on stage for the '1600' cast after it closed. Producers just don't do that.Now that Moss is gone he's the remaining real gentleman among producers."

"Carmelita" is about an Italian woman who during the war had three lovers in rapid succession and didn't know who was the father of her child. So she assumed the pose of a widow and spent the rest of her days praying daily for a departed husband who never existed. The moral is like that wonderful crack by Ruth Gordon on the Carson show on her age: "Don't face facts. They'll screw you every time." Georgia Brown will be the star and Jose Ferrer will direct.

It is a romantic musical of the style that went out of fashion in the late '60s. It's coming back, he thinks. "Whatever you may think of the show, 'Annie' is certainly a straw in the wind."

And it coincides with Lerner's going into a new period. For most of his career Lerner collaborated with persons of an older generation. That certainly never meant that his role was subordinate, but now an even greater burden for success or failure is on his shoulders. He thinks audiences will notice a difference.

"You do what seems right at the moment. We shelved 'My Fair Lady' for two years because a fairly cerebral musical without lots of secondary love subplots wasn't what was working then. We brought it out when that period seemed over.

"You have to go through a lot of self-doubt. And I hope it's not a selfdelusion. But I have this funny feeling I'm starting again now. See me in five years and Ill tell you if I'm right."