Joni Mitchell's career, from her folk singing days to her recent explorations into jazz-inflected rock, can be viewed as a quest for musical and psychological solidity. That is why Miss Mitchell, in her infrequent tours, can be counted on to revise her perspective toward the past, often revising the idiom of a song and even making lyrical alterations.

On Sunday at the Jones Beach Theatre, making her only local appearance since the release of her last album, WILD THINGS RUN FAST, Miss Mitchell extended that record's aura of confident exuberance to many of her older songs.

Playing the electric guitar with a quartet that included her new husband, Larry Klein, on bass, the keyboardist Russell Ferrante, the guitarist Michael Landau and the drummist Vinnie Coaliuta, Miss Mitchell took songs that were conceived with impressionistic folk-jazz and jazz-pop textures and smoothly translated them into harder rock numbers that retained a jazzy fluidity. These rockier arrangements were handsomely completed by the singer's forceful, emotional evenhanded delivery.

The years have been kind to Joni Mitchell's voice. Her girlish folk soprano has deepened and darkened into an interesting smoky alto that the singer wields with impressive subtlety and power.

In an evening with many surprises, the most startling performance was Miss Mitchell's revised Banquet, which was transformed from a modal art song into a sturdy hard rock anthem. As Miss Mitchell's phrasing has become more emphatic, her jazz singing has grown livelier, and her sharply accented renditions of the original God Must Be A Boogie Man and of the Motown standard I Heard It Through the Grapevine really swung.

Miss Mitchell's emotional poise and rhythmic assertiveness overcame any tendency to wallow in the lovelorn sentiment. This is not to say that such vintage confessional laments as A Case Of You, which she performed accompanying herself on the dulcimer, don't still carry an emotional punch; they do. But her mature approach, more analytical than impassioned, underscored the willfulness that underlies romantic obsessiveness.

One suspects that Joni Mitchell's songs like the paintings of Georgia O'Keefe, one of her inspirations, will continue to refract old obsessions in new and surprisingly interesting ways.