Pinchas Zukerman, one of the 20th-century's great solo string players, has broadened his musical activities in recent years to conducting and teaching, joining a pattern of virtuosos whose contributions to classical music shift and deepen.

Last evening with the National Symphony Orchestra at the Kennedy Center, Zukerman showed that his other activities have not diminished his renowned sound. He worked beautifully with Musical Director Leonard Slatkin and the ensemble, playing both violin and viola with that famously plaintive tone. Whether in the luminous fabric of Alban Berg's Violin Concerto or sailing through undulant lines of Hector Berlioz's "Harold in Italy," Zukerman invested his full energy, experience and intelligence.

With the spotlight so clearly on the violin, the evening's program began with Joachim Raff's unusual orchestration of J.S. Bach's Chaconne from the Partita in D Minor for Unaccompanied Violin, BWV 1004. The magic of the original version flows from the way Bach forces the player to draw out a dense orchestral sound from a lone instrument. Despite a polished performance and some novel colors, the assignment of the parts to various orchestra sections removed this exciting sense of physical struggle that is integral to the work's expression.

More revealing was the strong account of Berg's 1935 concerto with Zukerman as the soloist. The elegant Viennese composer partly dedicated the score "to the Memory of an Angel," which ostensibly refers to Manon Gropius, the dead daughter of Berg's confidant Alma Mahler. Yet this vibrant music -- etched in atonal yet highly poetic harmonies -- speaks on a range of deeper levels to Berg's complicated relationship with Alma, a clumsy if heartfelt love affair, and his own impending mortality.

From the mysterious opening of the first movement, Zukerman used his sweet tone and musicality to articulate Berg's rigorously constructed phrases. Surrounding these spectral violin lines was an ever-shifting sonic texture of harp, brass and woodwinds. While balances and rhythms could have been more carefully organized and tightened to bring greater clarity and focus, Slatkin elicited moments of raw power and pastoral loveliness.

In the alternately chaotic and solemn second movement, Zukerman brought as much dexterity to the devilishly difficult cadenzas as a feeling of rapt spirituality to the Bach chorale that Berg infused toward the concerto's closing. The musicians collaborated superbly in the soft last measures, which had all the feeling of a touching farewell.

After negotiating the angular concerto, the players reveled in the gentle repose of Berlioz's flowing "Harold in Italy," Op. 16. In contrast to the antagonistic interaction in a strict concerto, Zukerman's burnished viola worked more in tandem with the orchestra, especially the ethereal harp of Dotian Levalier. In this highly evocative performance that conjured sun-dappled images, the soloist radiated some beautifully floating melodies that seemed to spray gold across the Concert Hall.

This engaging encounter with the artistry of Zukerman and the NSO repeats tonight and tomorrow evening.

Pinchas Zukerman played both violin and viola with the NSO.