Although opera-ballet is often a synonym for conservative art, it's this kind of ballet that has been leading the Metropolitan Opera into some of its most adventurous programming.
Last year the Met offered a stunning tribute to modern French composers, which was conceived in part around a dance element. This season's adventure focuses on Igor Stravinsky, whose centenary will be celebrated in 1982.
The triple bill ranges from the cataclysmic ''Le Sacre du printemps'' to the charming ''Le Rossignol'' and ends with ''Oedipus Rex,'' an uncompromisingly formal oratorio. All three compositions were in one way or another connected with the great impresario of ballet, Serge Diaghilev, and all have continued to lure choreographers into extreme action, ranging from greatness to foolishness.
The Met was obviously looking for greatness in its handling of ''Le Rossignol.'' It commissioned none other than Sir Frederick Ashton to do the choreography. His dancers are no less distinguished. Natalia Makarova is the nightingale, and Anthony Dowell is the fisherman whose purity of spirit equals the purity of the nightingale's song.
Curiously, Ashton's work is neither great nor foolish. It's just wishy-washy. Rationally speaking, one realizes that Makarova and Dowell have extended dance passages and that they're on stage practically the whole time. Yet when ''Le Rossignol'' is over, it's as if the two dancers had been apparitions.
If Ashton did not rise to the occasion of ''Le Rossignol,'' Jean-Pierre Bonnefous did not sink as low as many choreographers have done when working with the score of ''Le Sacre du printemps.'' In order to get at the wild force of the music, choreographers have often resorted to violence, and cliche forms of violence at that.
Bonnefous's ''Sacre'' looks like a tea party in comparison. Instead of evoking images of prehistoric ape-men, Bonnefous brings to mind Russian peasants. Their movements are folksy rather than savage, and after the ritual murder is completed, one knows that the celebrants will be drawn back into their normal lives. This, after all, is a condition of ritual. Even if Bonnefous's ''Sacre'' misses Stravinsky's vitality, it strikes more truth than many of its fire-and-brimstone predecessors.