The pattern began early--around 1900, when Alma Winemiller and Johnny Buchanan were kids together in Glorious Hill, Miss. She was the preacher's daughter and wanted to talk about eternity--"Doesn't it give you the shivers?" He was the dcctor's son and his interests were more biological--"Let's kiss each other. Come on, Alma. Come on, let's try it."

As they grew up, Alma cultivated interests in poetry and Gothic cathedrals and music. She joined a literary circle and began to give singing lessons, and sometimes she would go to the window, hide herself carefully and peek out at Johnny, who lived next door and could sometimes be seen behaving scandalously. As if Alma didn't have enough problems of her own, what with emotional inhibitions and the pressures of a Victorian society, there was the added problem of her mother, who had drifted into second childhood and used her insanity with a kind of vicious calculation to humiliate her husband and daughter.

Johnny dated Alma once, after he finished his studies in bacteriology and was beginning to be known as Dr. John Buchanan Jr. He drove her to a casino "where anything goes" and invited her to join him in a private room upstairs. "You're not a gentleman!" she screamed, and she took a taxi home while John sought out easier conquests. But she continued to dream about saving John Buchanan, marrying him and building a life together, enjoying the respect of her husband, her children and the little community. "A man should have a lot more than respect for the woman he marries," John had told her, and she probably didn't understand what he meant.

The story is recognizably that of Tennessee Williams' classic play "Summer and Smoke," but when it is aired on PBS tonight (Channel 26 at 9:30; stereo simulcast on WETA-FM), something new will be added: music by Lee Hoiby that heightens the emotional impact of plot and dialogue, controls the pace of the production, eases the transitions in the show's very fluid structure and makes the play an opera.

It is curious that Williams, who is probably the most operatic American playwright of our time, has not received this kind of treatment more often--curious, at least, until you consider the economic problems of new operas in America. The fact is that a considerable repertoire of American operas has been developed by now, treating classics of our fiction and stage with the kind of care that Verdi and Puccini brought to the literary works of their period. The material from people like Tennessee Williams, Robert Penn Warren and Herman Melville is, on the whole, more worthwhile than the melodramatic claptrap found in most classical Italian operas. But modern American opera usually dies at the box office.

PBS and the Chicago Opera Theater have shown considerable courage and imagination in deciding to put on "Summer and Smoke" when they could have done another "Traviata" or "Bohe me" and received the routine approval of audiences already sold on that kind of material. This opera is a worthy addition to the repertoire; it is well done dramatically and musically; above all, it brings a distinctively American flavor to what is no longer an exotic art form. "Summer and Smoke" is one more step in the process by which opera is taking root in our country.

It deserves to be watched tonight, however, not for these worthy, musicological reasons but because it puts a completely absorbing and very rewarding two hours on the screen. The story of Alma and John captures a significant polarity in the soul of America: a life-crippling kind of inhibition that easily disguises itself as idealism, pitted against an equally crippling and compulsive self-indulgence that is its own dead end. This particular collision is presented with the flavor and style of a bygone time, but the personalities involved are permanent realities, taking up new slogans and issues in each generation to be used in their eternal conflict.

Lee Hoiby's music is in the neo-romantic vein, showing once again that there can be melody after "Che gelida manina." It seldom has the symmetrical structures of traditional opera, but its melodic impulse is constant, strong and flexibly adaptable to the shifting needs of the drama it enlivens. Conductor Robert Frisbie leads a well-paced interpretation with generally good singing and expert acting. Notable performances include those of Mary Beth Peil as Alma and Robert Orth as John, Diane Barclay in an inge'nue role and Charlotte Gardner as Alma's mother.