WHO BUT George Balanchine would have had the chutzpah? one couldn't help but ask. Who but this 77-year-old wunderkind of dance would have dared to end his own Tchaikovsky Festival not with a sumptuous blockbuster eliciting triumphant cheers, but with a somber phantasmagoria of a ballet that had the audience groping toward the aisles in hushed confusion and shock?

It was Balanchine's idea to have the New York City Ballet mount a Tchaikovsky Festival. He'd been talking about it for several years. It was time for a new festival in the rhythm of the company's existence, and what composers were left to pay homage to? They'd done Stravinsky in 1972, and Ravel in '75. Tchaikovsky was the logical successor, he declared -- who else had done more for ballet? The affair began with hoopla and glitz on June 4, the night of the inevitable "gala," and 10 days later, after more than a dozen world premieres by six choreographers, came to its astonishing end with a version of the composer's last symphonic testament, the Symphony No. 6 in B Minor, known as the "Pathetique."

It was a typical New York City Ballet -- and hence, Balanchinian -- conception. The first movement of the symphony was omitted altogether, it is one of Balanchine's articles of faith that the formalisms of sonata construction (the mold in which symphonic first movements are cast) do not lend themselves to choreographic treatment. The second movement, the "waltz in 5/4 time," was given a lovely, lilting realization by Jerome Robbins, with Patricia McBride and Helgi Tomasson heading an ensemble of six women.

The third movement, the gigantic march-scherzo, was a purely musical interlude, performed by conductor Robert Irving and the New York City Ballet Orchestra in a manner so lightly fastidious it sounded more like Mendelssohn than Tchaikovsky. Then came Balanchine's spectral denouement -- the dolorous finale, the "Adagio Lamentoso," the climax both of the symphony and of the festival and, quite literally, insofar as performance is concerned, a point of no return, since this was to be the movement's one and only presentation ever.

There had been some precedents in Balanchine's past -- the candlelit benediction he created to Stravinsky's "Requiem Canticles" in 1968 as a memorial to Martin Luther King Jr., performed once only; the exalted processional he made of the Choral Variations on Bach's "Bom Himmel Hoch" during the last evening of the Stravinsky Festival. Still, the "Adagio Lamentoso" seemed like nothing that had been seen on Earth before. It was less a ballet than a heaving series of tableaux vivants. These barefooted "mourners" in flowing green veils twisted and swooned through grieving masses of dancers, some in pale umber, some in scarlet, and then a hooded contingent in jet black.At one point, another group in white robes filed in slowly in prayerful attitude, holding flowers, enormous angel wings sprouting from their shoulders. The contingent in black sank to the floor, forming a massive cross; the cross heaved and rippled in ominous waves. At the rest of the figures left the stage in the increasing darkness, the child was left alone with the cross; he blew out the candle with the expiring bars of music and, in a narrowing spot of light, only the child remained visible. Curtain. A think patter of uncertain applause doubled off into the silence.

If you hadn't seen the choreographer's name on the program, you might almost have imagined this to be the work of Maurice Bejart -- of all people, Bejart, whose endless symbolisms, eccentric style and hyperbole have always seemed the antithesis of Balanchine. The three mourners in their diaphanous green suggested Isadora Duncan. The sculptural groupings of figures evoked Rodin. The lachrymose swayings of the ensemble echoed the strange idiom of the Eurythmeum Stuttgart, and somewhere well back in the shadows one could even detect the faintly messianic aura of Ken Russell. The miracle was that the experience remained pure Balanchine -- at once spiritual, austere and impassioned, indefinably but unmistakably Russian, dumbfoundingly original.

Instantly, of course, the buzz of interpretation could be heard everywhere. Some found the piece morbid, others ludicrous, still other depressing. Hidden parallels and conceits were drawn. Just as the Tchaikovsky exegetes had rushed to suggest that the "Pathetique" was the composer's Requiem for himself, so now the Balanchine diviners seemed sure the "Adagio Lamentoso" was both his swan song and his own funeral peroration.

As for Tchaikovsky, it must be said that more insupportable poppycock has been and continuews to be alleged about him than about any other musician in history, and "explanations" of the "Pathetique" remain perforce highly controversial Balanchine, it is true, having recently suffered a coronary and bypass surgery, must indeed be having some thoughts on mortality, as all of us do sooner or later, and there's no denying that the "Adagio" is a dirge of some sort. But it would be contrary to everything we know about the man -- his constitutional optimism, his confidence in life, his hardheadedness -- to suppose that he has suddenly gone all mushy and self-pitying, even subliminally.

Great art enjoins us from making simplistic identifications between the creator and the created: the Shakespeare who gave us "Lear" also gave us "The Tempest," and the Balanchine who also newly confected the intricately euphoric "Mozartiana" for this festival, as well as several lesser items, and the profoundly poetic "Davidsbundlertanze" not long before, doesn't appear to be someone ready to give up the ghost. It would be far more in keeping with Balanchine's historic trajectory to view the "Adagio" as an elegy for the lost world of Tchaikovsky and Petipa, and to see Balanchine as the child who has risen upon their graves. The trio of mourners wears green, the color of spring and rejuvenation; the final image one sees is not the cross or crypt, but the child.The music may end in desolation, but the ballet affirms the continuity of art.

Aside from his persuasive contribution to the "Pathetique," Robbins also came up with an exquisite, if close to saccharine, pas de deux set to the slow movement of the First Piano Concerto, among other things, and one major work -- the "Piano Pieces," surely destined for a secure place in the company repertory. Set to a selection of mostly little-known and grossly undervalued keyboard works, it's a charming, lavishly inventive ballet very much in the manner of "Dances at a Gathering" in its companionability and folk coloration. For all its masterly resourcefulness, however, it lacks an ultimate quality of surprise -- the kind of jolt we get from Balanchine in a work like the "Adagio Lamentoso." Audiences may well find novelties within it, and the invention is real, but one also senses that for Robbins this is terra cognita -- he's been around this course many times before.

The other strongest candidates for survival from this Tchaikovsky Festival came from the hand of the company's brilliant principal dancer, of late also turned choreographer, Peter Martins. His craftsmanship gives every sign of steady increase. He now seems able to handle large-scale structures like the Symphony No. 1 ("Winter Dreams") and the "Capriccio Italien" with unforced authority, and minus the didactic edge that undermined some earlier efforts.

Martins gives us a coup de theatre of his own in the ending of the symphony -- just at the point where one would expect a colminating crescendo, the ensemble and then the soloists retreat to the wings and the grand coda is played to an empty stage. People were heard wondering if he'd had time to finish the ballet, but it seems clear the stroke was intentional, as if Martins were telling us, "As much as I admire Balanchine, there's no point in my trying to duplicate his best known effects -- here's something of my own to send you away thinking, maybe about the whole relationship of dance to musical score." The "Capriccio," a double-barreled tribute to Balanchine and Bournonville, has a blustering exuberance about it; in one striking passage, columns of dancers tossing their beating lets to opposing sides suggest the jubilant swing of cathedral bells. Still, something of a chill Danish wind blows through these pieces; Martins has learned both how to intrigue and how to entertain, but not yet how to move us.

The rest of the Festival offerings, for the most part, served only to illustrate how burdensome it must be to labor in the penumbra of a Balanchine and a Robbins. One particularly painful case was John Taras' "Souvenir de Florence," which had all the hallmarks of the Balanchine methodology except the enlivening spark -- it was all so admirably bricked together, and yet about as stirring as a row house. Jacques d'Amboise's miniature "Scherzo, Opus 42," however, proved to be a nice bit of mischief -- the bizarrely scampering ensemble of males teasing Patricia McBride bore a family resemblance to the goonish drinking companions of "Prodigal Son," except that here the tone wasn't insidious, just raffish.

It's too soon after the fact to estimate the durability of the Tchaikovsky Festival residue in the long run, but it seems fair to say that though it may be understandably less imposing than the fabled Stravinsky Festival, it looks far more fertile in retrospect than the Ravel Festival turned out to be. Perhaps the thing most to be lamented is the vast sum spent on Philip Johnson's modular plastic set, which succeeded only in turning the art of scenic design into a species of interior decoration -- and dispiritingly brittle decoration at that. On the other hand, none but the least charitable of hearts would begrudge the New York City Ballet even a costly peccadillo or two, where so much choreographic enrichment is at stake. A last request: Couldn't we have the "Adagio Lamentoso" back a few more times, instead of wrapping it forever in the shroud of oblivion?