The D.C. Youth Chorale Program is 20 years old this year, and its alumni are making music on stages throughout the world, some with glorious success. Several of them were on hand yesterday at the Kennedy Center's Terrace Theater to join in an anniversary celebration but, exciting as their various performances were, the greatest testimony to the worth and artistry of the D.C. Youth Chorale is the chorale itself.

Soprano Wilma Shakesnider is one of these renowned alumni. She was magnificent, several years ago, in the Houston Opera's production of "Porgy and Bess." Yesterday, singing through a bad cold, she proved that her artistry extends to the French, German and Italian repertoire as well. Shifting from style to style and emotion to emotion like a virtuoso chameleon, she displayed impecable musicianship and superb diction.

Dancer Vincent Wineglass, who also received his early musical training in the chorale, presented a much-too-brief example of his own lyrical choreographer of music by Debussy. And the "Zuri Watu" Dance and Instrumental Troupe, guests artists, performed a colorful set of Yoruban tribal dances and chants.

All of this was prologue to the main event, however. Under the direction first of current conductor Edward Jackson, and then of the founder Frances W. Hughes, the D.C. Youth Chorale put on a show that projected energy, splendid training and a high degree of musical distinction.

With Hughes on the podium, they swung through music by Duke Ellington and arrangements of folk songs and spirituals. Soloists from the chorale itself were impressive.

The Elementary and Junior Division Choruses joined their elders in singing the concluding "No Man is an Island."