Palms up, her hands floated at her waist, barely touching. Her curved neck was soft, yielding; her eyes downcast. She was Giselle.

In an instant her chin lifted, her neck grew long and lithe, she looked down through half-closed lids.Her wings flashed up, her feathers barely shivering with the aftershock. She was Odette.

And in the next second, her jaw clenched like a fist. The lines beside her throat and into her shoulders were rigid. Her elbows and wrists angled sharply, her lip curled: Carmen.

With all these characters, Alicia Alonso, prima ballerina assoluta and head of the Ballet National de Cuba, stood alone on the stage of the Kennedy Center's Terrace Theater. She wore a pantsuit, low-heeled sandals, and a scarf, but from moment to moment she seemed to be wearing soft chiffon, gypsy rags, milk-white feathers.

Suddenly, her mouth twisted and she looked out into the audience.

"I don't do the whole ballet," she mock-scolded, her Cuban accent nearly erasing the "t" in "don't." "You come tomorrow night to the performance."

Alonso, currently appearing with her Ballet Nacional at the Kennedy Center, was demonstrating to a nearly packed house and interviewer Walter Terry how characterization depends upon physical articulation. "I don't think only feathers can make you a swan," she laughed.

She posed in the classical manner, in the romantic mode, a la Antony Tudor and Agnes de Mille. She walked, stretched, framed her face, turned her wrist in a myriad of subtle, expressive ways. Then she laughed, remembering how pantomine can run away with the dancer.

"My dancers, they liked the swan arms so much," she began, her liquid arms beating and trembling, "that all of a sudden they were doing 'Nutcracker'!" and her stiffened arms quivered frantically.

As the audience of balletomanes laughed, she added, "The feet, the extension was fine, but the position of the arms, the head, the body, they change-and you cannot fly in every ballet!"

Alonso called Tudor's choreography "very concentrated, from inside" - patting her diaphram - "outward." In contrast, De Mille's was external, powerful, weighty.

"Oh, when I used to finish Lizzie (Borden), people used to run!" she recalled.

Lizzie Borden so overpowered Alonso that one night, she said, striking her ax against a prop tree stump, she actually split the stump and froze stunned.

Last night's interview-demonstration was the fourth and final in a series of Terry interviews with guest ballet stars, a series the Kennedy Center hopes to continue next season.

Terry, the grand old man of ballet criticism who looks like a cross between Alfred Hitchcock and Orson Welles - in a pink neck scarf - is now 66. Alonso is 58. As a young critic at the Boston Herald, he first saw her in 1938.

"You may think I saw her back in the corps de ballet of 'Swan Lake' or 'Giselle,' and over the years watched her develop," said Terry in his introduction."But she was toward the end of the line, tap-dancing in 'Stars in Your Eyes' with Ethel Merman." CAPTION: Picture, Alicia Alonso and Orlando Salgado in "Carmen."