What, why and how are the questions that must be addressed before anything of value is pursued. At 19, Charles Curtis has already mastered the hows of cello playing and is well on his way to the whats and whys.

At the National Institutes of Health yesterday, he dispatched the familiar Freschbaldi D Major Toccata boldly with broad strokes, explored some of the subtle delights of Beethoven's Variations on a Handelian theme and brought a fresh directness to the marvelous Debussy sonata. If he has not yet burrowed very deeply beneath its surface, his reading showed an understanding that is far from dogmatic and leaves him plenty of room for development. His performance of the Barber sonata was big and lyrical and the works by Cassado were nicely handled.

Curtis seems to be a natural. His playing appears effortless. This is dangerous only if it is truly so: The direction and extent of his artistic development depend on the continuing maturing of his understanding and imagination. This is hard work.

Accompanying Curtis on the piano was his brother, Henry, 22, whose playing, while not as brilliant, was in some respects more completely internalized and poetic than his brother's.