"An Evening With Shaun O'Brien," at the Smithsonian's Carmichael Auditorium last night, was a diverting and instructive glimpse at a side of ballet seldom in the limelight these days -- the creation of character roles, especially those crucial roles that give dramatic ballets their special pungency and atmosphere.

O'Brien, who coincidentally celebrates his 59th birthday today, has been a member of the New York City Ballet since 1949, and particularly in recent decades, he's come to personify the mastery of characterization demanded by his specialty -- such parts as the mysterious, eccentric toymaker, Drosselmeyer, in "The Nutcracker," or that somber patriarch, the Father, in "Prodigal Son."

After a brief introduction and an annotated showing of slides illustrating O'Brien's portrayals over the years, the actor-dancer came to the heart of the evening -- a thumbnail demonstration of how he transforms himself for the stage with the help of makeup, costuming, facial expression, gait and gesture. Though he also performed brief scenes, the depictions were necessarily limited by the restricted scope and facilities of Carmichael -- a grand piano served O'Brien as a dressing table, taking up much of the small space.

O'Brien's performing artistry is wordless, but in this context he proved as articulate and witty in speech as he is in movement. His first example was the inscrutable Baron in "La Somnambula" -- the "strangest of all characters," as O'Brien put it -- who is whipped into a jealous rage by the Coquette and rushes off to stab the Poet who has fallen in love with his sleepwalking wife. O'Brien showed how he gives the character a large nose -- fashioned from mortician's wax -- for strength, and eyebrows to form "an expression somewhere between elegance and cruelty." "I'm making a face larger than life for a character larger than life -- almost a mask," he explained.

In Balanchine's "Coppelia," Dr. Coppelius the dollmaker is "a loner, a self-deluded searcher for secrets of immortality, a genius, but mad," O'Brien observed. He proceeded to provide himself with a crooked nose "maybe broken by peculiar experiments"; a sallow complexion because "he's locked in his lab all the time"; eyes "red from sleeplessness and reading strange books," and other features, each with its own detailed dramatic justification. As a lighthearted coda, O'Brien metamorphosed into the fop Leandre in "Harlequinade," the rejected suitor whom O'Brien calls "the eternal dilettante, the pretentious dandy."