Joni Mitchell and The Persuasions.
At the Fredric R. Mann Music Center, 52d st. and Parkside ave., Philadelphia.

Joni Mitchell has been walking the line that separates pop stars from serious artists long enough to slip comfortably from side to side, and in her appearance last night at the Mann Music Center she demonstrated how a truly original talent can have its cake and eat it too.

The cake in this case is the not-so-popular frontier of progressive jazz, a territory Ms.Mitchell has set her sights upon since she began to outgrow the linear terrain of her folk music roots. By now, Ms.Mitchell has fully thrown over her acoustic guitar for an electric one, and has assembled a challenging band of jazz-fusion musicians. Her music proves more than a match for their inspirations, but her glamor is what bridges the gap between the art she creates and the entertainment she provides.

Last night's loudly admiring capacity audience seemed perfectly suited to Ms.Mitchell's designs and eagerly followed her to all sides, responding no less appreciatively to her artiest new songs than to the enchanting pull of her physical presence. In a silky black and red ensemble, the slim, high-cheekboned, curly blonde Ms.Mitchell was the shimmering symbol of the remote sensitivity and finely tuned sexuality her songs so often depict, and she was also breaking artistic ground.

Her current stage show is an exercise in musical gear shifting- from the lilting pop-rock romance of "Free Man In Paris" or "Raised On Robbery" to the stark, haunted lyricism of "Amelia" or "Hejira," and, ultimately, to the demanding jazz sonorities and rhythms of her most recent compositions, most of them written in collaboration with the late jazz bassist-composer Charles Mingus.

Indeed, her pristine soprano may seem all too suited to the gliding melodiousness of her folk-rock-pop, but it's no less effective as a swooping, scatting, stacking jazz instrument. Mingus' music has forced her phrasing into new corners and over strange edges, and Ms.Mitchell has met teh challenge with poetry and imagination equal to the task.