The one-man show is now a common occurrence on our stages and, given the economics of show-biz, is likely to become more so. But Emlyn Williams, who opened his "Dylan Thomas Growing-Up" last night at the Kennedy Center's Terrace Theater, is something still quite uncommon -- a one-man extravaganza.

The stage is almost bare -- a carpet, a chair, a few bedraggled notebooks and scraps of paper that he carries onstage but does not consult except as props in his long, kaleidoscopic monologue. All that is offered for the rest of this month in the Terrace is two hours of purple prose (and a few minutes of verse) that you could probably buy in paperback for less than the cost of a ticket. That and the delivery of Emlyn Williams -- which, of course, makes all the difference.

Dylan Thomas is dead now a quarter-century, and even when he was alive, at the height of his fame, he seemed an odd sort of superstar -- an anachronism. As a prose writer, he was soft-edged and given to fantasy in an age of realism, a word-weaver drunk on rolling syllables in a period dominated by the flat, no-nonsense style of Hemingway and the tortured dialectical syntax of Faulkner. As a poet, he had an odd taste for rhyme and formal structures and resounding, rhetorical statements when the approved style was elliptical, metaphysical, crabbed and jagged. He was, when you come down to it, pretty -- and he intoxicated a generation that thought it had outgrown prettiness.

His magic in life is also the secret of his success in the reincarnation that Emlyn Williams brings to town. His books are all right, but not the real Thomas. He lived, and he lives still, as a bard, a storyteller, a man who uses not the cold printed page but the breath of life to make words work. On the brink of the audio-visual age which would later be charted by McLuhan, Dylan Thomas was the new apostle of the spoken word.

Williams makes no effort to imitate Thomas. It would be futile if he tried; the man's original voice still lives among us on his recordings, and his image is still vivid in the minds of many who saw him. This neat old man with perfectly groomed, snow white hair, quietly clad in a business suit and tie, bears no resemblance at all to the tempestuous, rumpled young poet except for a slight trace of Wales in his voice. But his ambition goes beyond depicting a single person, even one as multifaceted as Dylan Thomas. In the course of the evening, Emlyn Williams is dozens of people, each subtly characterized in voice and gestures, often performing in duets or trios.

He is a knee-high child sitting on a fence watching cows in a pasture while his uncle and a busload of cronies drink a pub dry; he is the uncle, enormous and roaring drunk, and the aunt who has to climb up on a chair to hit the uncle with a china dog, as she does ritually on Saturday nights. He is a lonely young man, standing under a railroad arch -- and he is the arch, shaking as a train goes by.

He dances a polka sitting down, and he flies, tiptoe, in a childhood fantasy, banking and turning in great loops to catch the scenes below -- more convincing, for a moment, than the people who really fly in "Peter Pan." He is a schoolboy, fighting with a new friend and yearning to throw a rock through a neighboring window, and a very old schoolmaster with palsied hand and quavery voice remembering the poet as an undistinguished child: "His first name was uncommon, but he was not."

It is superb material for the Terrace, with its intimacy bringing the slightest gesture into close-up, its clear acoustics sensitive to the smallest vocal nuance.

The material is a celebration of the commonplace, childhood concerns and fanatsies that anyone will recognize and it demonstrates finally what strangeness there is in the commonplace. There is another, darker side of the poet's life, barely hinted at here in an ocasional passing shadow -- such as the concluding selection, "And Death Shall Have No Dominion." "Dylan Thomas Growing Up" is a triumphant affirmation of life, and that is surely the way Thomas would have wanted it.