As is the custom in the Kennedy Center Concert Hall, latecomers last night were kept waiting in the lobby, where they could watch the concert on closed-circuit TV until the first break came in the music. In this concert, that meant waiting outside for more than an hour until the extraordinary sitar virtuoso Ustad Vilayat Khan paused to catch his breath.

Then there was a mass entry, while Vilayat sat not very patiently, flanked by his 13-year-old son and student Hidayat and percussionist Zakir Hussain, waiting for the hall to settle down so he could start again. Once calm was reestablished, he picked up where he had left off in a long, intricate, improvised musical dialogue with Hussain, occasionally accepting a glass of water from his son with his left hand while he continued to play with his right.

All told, he performed at a high level of concentration and virtuosity, with only that one brief pause, for nearly two hours before the intermission. It was one of the year's more remarkable demonstrations of musical skill and concentration in this city.

This was Vilayat Khan's first Washington performance (on his second American tour) in a career that began more than 50 years ago when he was only 6. The evening revealed not only a great artist but a remarkable audience in a city not noted as a center of Indian music.

The audience was clearly as important as in jazz or flamenco music, two art forms that have a peripheral resemblance to Indian music. As rapport was established between the musicians and the audience, the music became more elaborate, more brilliantly daring, while remaining always within the boundaries that had been implicitly set down at the beginning of the piece. If the musicians had not drawn strength from the audience's support, they could hardly have continued to perform so long at such a level of intensity.

The players also drew inspiration from one another, like jazz players in a duet improvisation that is at once collaboration and competition. Vilayat spun out unexpected changes of melodic direction, sudden pauses, shifts in dynamic accent, trying to catch Hussain off balance. But the partnership was flawless and their mutual appreciation was evident and musically productive.

Vilayat makes his instrument sing with the eloquence of a human voice, trembling on the brink of words. He also makes it produce musical sparks like a fireworks display. He will be most welcome on his next visit