The Night of the First Americans, last night at the Kennedy Center, was certainly one of the most unusual performances yet seen in the Opera House. But by the time it was all over, the basic form and style of the evening seemed somehow appropriate. To celebrate the heritage and talent of original Americans, the evening slipped into one of the few original American art forms: the television variety show.

Beyond a tendency to mild nostalgia in the first half and mild militancy in the second, the evening seemed to lack thematic coherence. On the other hand, it offered something, somewhere in its long course, for almost anyone to enjoy. The dancing was good in many styles from traditional ceremonies to modern ballet, music by Stravinsky and choreography by Maria Tallchief. Otherwise, the best moments seemed to come near the end: first a haunting trombone solo and vocal on "Just a Closer Walk With Thee" by Big Chief Russell Moore that seemed impromptu, and a few minutes later a duet on "You're Nobody 'Til Somebody Loves You" by Sammy Davis Jr. and Wayne Newton that really was.

At the end, it was almost impossible to bring the curtain down. The whole cast on stage for their final bows, kept on dancing; they didn't want to stop and nobody in the audience seemed eager to leave.

But in spite of a strong close, the evening was spotty. It ranged from Loretta Lynn singing "Coal Miner's Daughter" to Bonnie Jo Hunt singing the "laughing song" from "Die Fledermaus." It is hard to imagine that many people in the audience enjoyed both equally.

Specifically Indian material, as compared to Indian performances of other material, came mostly near the beginning of the evening. Some of it was very beautiful, particularly the movements of the Ponca Dancers in their feathered costumes and the deep, simple telling of an Ojibway creation myth by Eddie Benton and the Red School House Kids. The most successful adaptation of Indian material into a more common idiom was probably in the work of Paul Ortega, who blended country and travel styles in a haunting mixture.

But mostly, it seemed like the sort of thing you can see on television almost any evening. The effect was particularly striking when a large screen was lowered and Jonathan Winters was projected on it, live from California, doing a comedy routine on Indian themes. Or later, when Dick Cavett appeared on the same screen to introduce and comment on a sequence of film clips showing stereotyped treatment of Indians. The same screen had one of its finest moments when it was occupied by Will Rogers, one of the first Indians to score a major success in American show business, and the tone of ethnic pride that pervaded the evening may have been summed up most effectively in his familiar joke: "My ancestors didn't come over on the Mayflower, but we met the boat when it landed."