Nothing sums up quite so dramatically the phenomenal range -- the completeness -- of Ludwig van Beethoven's musical mind as that triptych of spiritual masterpieces that comprised his last three sonatas. Like the final three Mozart symphonies, they are thought of together because each seems a final summation of personal themes recurring throughout each master's career.

Thus Peter Serkin, one of the most insightful and eloquent of Beethoven players, grouped the sonatas in sequence for his concert last night at the Kennedy Center's Terrace Theater.

Each work is as much a philosophical drama as a musical drama, each intensely personal. Written near the end of his life, the sonatas are valedictory -- composed in the austere late Beethoven harmonic vocabulary that always seems to suggest so much more than explicitly said.

The two-movement final sonata, No. 32 in C minor (Op. 111), distills the idea the most starkly -- the violent storm of the opening movement expressing the ravages of life, and the lengthy, sublime theme and variations expressing a vision of peace and reconciliation that is unexcelled in all of music. There is no work by Beethoven that says more than this one, or that says it more perfectly.

The other two sonatas are similar in design, each ending in a massive final movement that seems the composer's last word on its theme.

What most characterized Serkin's performances was a muted intensity that kept one's concentration on the mysteries behind the music and seldom brought attention to his actual playing, which was phenomenal. There was often a hushed quality to these performances. The effect was of increased tension, especially in the quiet sections. Serkin's soft playing in the treble was especially controlled, making it possible for him to play in notably clear relief those complex passages where Beethoven may have four or five separate lines going simultaneously.

Articulation was so fine and pulse so steady that the instant switches of mood with which these works are riddled fell easily into place. Thus the works seemed less schizoid than they do in some hands.

Of these three great finales, the theme and variations that end the Sonata No. 30 in E (Op. 109) -- a poignant statement of faith -- had a particularly remarkable balance of emotion and intellectual clarity in Serkin's performance. He took all three finales very slowly, and amazingly steadily.

The last pianist before Peter Serkin to play these three sonatas in one recital at the Kennedy Center was Rudolf Serkin. The styles of the two are quite different -- the father choosing a more magisterial approach, the son a more fluid one. What they have in common, though, is a single-minded dedication to Beethoven's intent that few other pianists anywhere could begin to match.