One of the many nice things about the "Festival of the Nile," the potpourri of Egyptian dance, song and music at the Kennedy Center Concert Hall last night, was the feeling of unadorned authenticity of the troupe. This wasn't one of your highly packaged, commercialized ethnic spectaculars, which so often turn natural charm into glitzy and artificial theatrics. The show, which was concluding its first American tour in Washington, looked like something you might encounter in the streets of Cairo or in a desert encampment, and, in fact, the majority of the performers, ranging in age from youths to septuagenarians, weren't schooled professionals but native entertainers.

All the same, the event worked splendidly as theater, despite the uncommodious setting of the Concert Hall, with its coldly barren look and lack of stage facilities. A hugely enthusiastic and partisan audience filled the seats -- it was reminiscent of the era when the Washington Performing Arts Society's folk dance series packed this hall consistently for close to a decade. It was also the kind of crowd that felt itself a part of the performance from the start: No sooner did the colorfully clad drummers, singers and dancers march in for the opening wedding procession ("Zeffa") than cheers and huzzahs broke forth, and numbers of people clapped vigorously in time with the rippling percussion.

The core of the troupe came from the Samer Company of Cairo, but director Abdel Rahman El Shafie also recruited performers and material from many regions -- the Nile valley, the coastal plains, Nubia in the south, the great deserts and oases -- to illustrate the cultural diversity of a nation that has been one of history's crossroads since the birth of civilization.

The dance types ranged from the Raqs Sharki -- what Westerners refer to as "belly dance" -- to a rite of exorcism, dervish-like spinning by broad-skirted men, a "stick dance" representing a stylized combat said to hark back to Pharaonic times, and startling feats of dynamic balance, such as a woman raising a chair aloft with her teeth, or gyrating with a many-tiered, lit candelabra resting on her head. No less engrossing was the music -- songs of love, lamentation and revelry, with their characteristically tart, quivering ornamentation, and a fascinating array of indigenous instruments ranging from penetrating reedy winds, to a two-string violin, to a wonderful battery of drums, tambourines and finger cymbals.