AS A CHILD, I remember listening to records of Dylan Thomas reading his own poetry. The voice on those records was deep, hypnotic, musical, but the poetry it crooned seemed incomprehensible. While the rhythms and cadences of the poems held me, the language that contained them, so dense and rich, wove into a fabric of meaning no child could understand. What stayed with me instead was the voice itself.

Emlyn Williams's one-man show, Dylan Thomas Growing Up, similarly impresses me as a collection of voices--all creations of Williams's own hypnotic baritone. In contrast to The Belle of Amherst, Julie Harris's recent tour-de-force portrayal of Emily Dickinson, Williams has steered away from constructing a coherent dramatic whole, embracing a well-developed set of invisible characters, a climax and a denouement. Instead, he uses only a loose chronological organization, modeling his entertainment after Thomas's own prose, with its fluid structure and its lack of a clear beginning, middle and end.

Drawing almost exclusively on Thomas's prose, including A Portrait of the Artist as a Young Dog and Quite Early One Morning, Williams sifts with poetic brilliance through the author's memories and fantasies of childhood. These emerge as a series of sharply recollected details amid word paintings of character and scene. Plot is virtually non-existent, but the details themselves are indelible. Bob the embezzler is a "small absconding man," who under accusation smiles "like a razor." One woman is observed to have "painted her face as though it were a wall." Thomas himself is described as a "bombastic adolescent provincial bohemian," for whom lying was good, because "it made you feel warm and shameful."

As theater, Williams's compendium of Dylan Thomas tends to be overly static, with little movement, either physical or dramatic. Sound and lighting instead become all-important--sound lulling us into acceptance of the comic and celebratory world of the sketches and stories, lighting marking changes of mood within this world and signalling breaks between tales.

There are further grounds for complaint, if only about Williams's intent. Describing his aims, Williams has written that he wanted to present "a warm and richly comic side" of Thomas "which is beautifully at home in the theatre." His concentration remains purposely on Thomas as storyteller; but his powerful readings of the only two poems he recites, "The Hand that Signed the Paper," and "And Death Shall Have No Dominion," made me wish he'd included more. Williams presumably feared, not without reason, that much of Thomas's poetry would prove as inaccessible to a theater audience as it did to me as a child; still, it's hard to imagine a picture of Thomas's childhood complete without "Fern Hill."

IF WILLIAMS the playwright errs, Williams the actor compensates for his failings. He is superb. His exquisitely nuanced expressions, as well as the ventriloquistic ease with which he mimics the voices of Thomas's friends and family, are spellbinding even when the material itself is not. In the overly long first act, Williams sketches, among others, the portraits of Cousin Gwilym, who writes love poetry to Jehovah, and Thomas's young friend Dan, who authored seven historical novels before the age of 12. ("Just early stuff," he remarks modestly.)

The second act begins with a neat comic sketch called "Reminiscence of a Schoolmaster," who says of Thomas that "his first name was uncommon, but he was not." The show's most prolonged success, however, is Williams's rendition of the very funny "Adventures in the Skin Trade," during which his capacity for mimicry and elegant comic timing find their fullest expression.

Insofar as Dylan Thomas Growing Up has any message--beyond the author's own rich appreciation of childhood innocence, those days when boys exulted in "inaccurate" drawings of naked girls--it comes in the show's final moments. As Williams walks offstage into darkness chanting the famous "And Death Shall Have No Dominion," the lights come up on his storyteller's chair, now holding only a set of battered manuscripts. The device and its meaning--the immortality of art after its creator's death--are predictable enough; their sudden effectiveness here is a measure, perhaps the very best, of the extent of Williams's achievement.