Klaus Tennstedt's baton technique has not improved since the last time he conducted here. He still holds his elbows out at an awkward angle, and his arms still flap like wings when the excitement of the music carries him away. His beat often looks almost unreadable, at least from the audience.

Sometimes that baton moves in what look like meaningless circles, and sometimes it comes completely to rest while the music continues at a steady pace. Sometimes his hands seem to be modeling the music, like an immense ball of clay being formed into a sculpture. With his tall, thin body in tails and his arms moving up and down, he sometimes resembles a giant bird hovering over the orchestra.

The bird image was reinforced audibly in the music that poured forth from Tennstedt and the London Philharmonic Saturday night at the Kennedy Center. He was a songbird, producing sounds that seemed at the same time deeply thought out and totally spontaneous. They were sounds of enormous complexity, particularly in Mahler's Fifth Symphony. They were rich in emotional shadings, ranging in dynamics from the tiniest whisper to crashes of percussion thunder. But they flowed as simply and naturally as the music of a lark or nightingale.

Tennstedt and this orchestra, which seems to have a telepathic rapport with him, function at a level of sophisticated ease that makes the most challenging music seem as elementary as playing simple scales. The closest approximation I can recall hearing in the Kennedy Center is the late Karl Bo hm conducting the Vienna Philharmonic.

The program opened with Schubert's "Unfinished" Symphony, ideal music to set the evening's tone of thoughtful lyricism. The performance was perfect. Not a note in this ultrafamiliar music sounded routine; it was as though the musicians were encountering it for the first time, but had been born knowing how to play it. The interpretation was personal, not quite like that of any other conductor, and while it was happening it seemed exactly right.

But the Mahler was the real showpiece -- deeply tragic in its opening sections, brilliant in the pivotal Scherzo, bursting with joy at the end. It was played with an intensity of feeling, a polished ensemble sound and a sensitivity to the music's many changes of tone and pace that were all breathtaking. Tennstedt's next visit to Washington is already eagerly awaited.