It's been almost a decade since Joni Mitchell reached her commercial - and arguably, artistic - peak with the 1974 release of her acclaimed Court and Spark LP and its hit singles Help Me, Raised on Robbery and Free Man in Paris.

Shortly thereafter, however, she all but abandoned the successful pop formula she'd developed for experimentation with traditional jazz forms.

In the process she also diluted her huge mainstream following - not only on record but in live performance as well.

The fact is, however, that despite the turn-off triggered by the jazz influence in her albums, her concerts retained the quirky, understated appeal that's been a trademark throughout her nearly 20-year career.

Combining a shy, coltish sexuality, a unique, imaginative flair for music and a smoky but penetrating voice that's as impressive with pop and rock as it is with jazz, reggae and R&B, she commands an appeal so charismatic that it transcends musical boundaries.

Still, only about 5,000 obviously hard-core Joni Mitchell fans showed up for her performance at Blossom Music Center.

She didn't disappoint them.

Backed by a fine four-piece band that featured bassist-husband Larry Kline, Miss Mitchell - alternating on guitar, piano and Marlboros - put together a terrific two-hour and 15-minute show of material from all phases of her career, including her new, far less jazz-oriented LP, Wild Things Run Fast.

Dressed in a putty colored blouse, long skirt cut just above the ankles and high-heeled black pumps, with her blonde, shoulder-length hair falling in tangled curls, she didn't look like someone who would have an electric guitar hanging from her shoulder.

But with the first strains of the bounding Coyote it all made sense.

With the audience obviously on her side, she hit stride early. Into her second song, Free Man in Paris, and the catchy dance number Cotton Avenue, her movements were already becoming more rhythmic and spontaneous.

By the smoldering Sharon and into the sing-along God Must Be a Bogey Man, her nods and impish smiles indicated she was enjoying herself as much as the crowd which, justifiably, seemed to be a lot.