For a woman who loves to dance, Joni Mitchell - surprise - takes herself pretty seriously. "I'm an artist," she explains. "What is an artist's pursuit? It's always been the same thing - truth and beauty. If you hit that truth, that's the stuff of art. Gossip is trivial next to the work, but that's what this society responds to."

Mitchell pauses and finds a target as elusive as a BMW in Beverly Hills. ''And what do the people know of art?" she says. "Only a handful of people understand the work."

Joni Mitchell can be excused a little testiness. First off, television's thirtysomething has played "Circle Game" enough times to make a hippie plead for mercy. But mostly, nobody will let the singer-songwriter forget her confessional classics - Court and Spark, For the Roses and, especially, Blue.

Mitchell, like Neil Young a lone wolf from Canada, is an artist who has left an indelible print. She's danced along the fall line of pop culture for 20 years, and is fully cognizant that her first decade remains the root of her fame. At the same time, she's tasted both the sweet wine and sour apples of celebrity, and thinks her more recent work is just fine.

The new Chalk Mark in a Rain Storm is Mitchell's 15th album, and like almost all of those that preceded it, it sounds different from the one that came before.

"I don't think my themes overlap greatly," she says. "If you look at all of my work, you'll find a diversity of theme, and texture, and instrumentation. As artists go, I'm almost too mutable for most people. I'm restless, like Picasso."

Mitchell calls Chalk Marks "a combination of jazz vocalizing with a touch of rhythm and blues." Somebody else might hear a style that reflects both the restless musicality of 1976's Hejira and the high-tech pop of 1985's Dog Eat Dog.

The first thing people will notice about Chalk Mark is its cameo voices - Peter Gabriel, Willie Nelson, Tom Petty, Don Henley and Billy Idol. Yes, Billy Idol. Mitchell explains her rationale succinctly - "I cast voices the same way you'd cast a face in a film" - and can't understand why people might think her choice of co-stars peculiar.

"This has happened all through my career," says the singer with some irritation. "Crosby, Stills, Nash and Young. James Taylor. My generation was hippies back then, and we worked together. Nothing has changed."

Mitchell, who wrote "Woodstock," knows better than that. After all, they weren't called Crosby, Stills, Nash and Idol. Still, the ecological and ''study-war-no-more" social concerns of Chalk Mark do form a bridge to the kind of socially conscious folk-rock of the hippie heyday.

By contrast, for much of the past decade, Mitchell's music has had the instrumental trappings of jazz, though her winsome voice and idiosyncratic writing style have inevitably personalized any genre with which she's worked. Mitchell says she really discovered the blues through Mingus (1979), her collaboration with the jazz bassist and composer Charles Mingus, who was then dying of amyotrophic lateral sclerosis (Lou Gehrig's disease).

"In the coffeehouses when I began," says Mitchell, 44, "players divided themselves into two camps. The Gibson players played the blues and the Martin players played English ballads. I was in the Martin camp, and the blues to me seemed simplistic for my taste. But after working with Charles on a piece like 'Goodbye Pork Pie Hat,' I began to come around. The simple blues were opened up to me through these complex blues."

Mitchell used to sing the romantic blues; in 1982 she married her bass player, Larry Klein, who helps produce her albums. (The guitarist seems drawn to bass players - before she worked with Mingus, the most dominant instrumentalist on her jazz-inflected albums of the late-'70s was electric bassist Jaco Pastorius, who recently died in Florida.)

"We're a mom and pop business," says Mitchell, discounting any undue tensions arising from mixing business with pleasure. "We get along great. My husband is a reasonable person. We have constructive arguments, and we clear the slates so there's no garbage piling up. We're able to admit our mistakes and back off when we perceive we're contributing to the difficulty.

"I've been married to the man for seven years," concludes the former pop princess of lonesome angst, "and I'd marry him again in a minute."

Mitchell wasn't always the marrying kind, although she was married briefly in the mid-'60s to folk singer Chuck Mitchell. She was romantic but restless, and her personality shone in her music; after three albums of more traditional songs, Mitchell pursued a more deeply personal style of verse.

"All fiction writing touches on autobiography," observes Mitchell, acknowledging that she did more than touch during the years when her writing virtually created the notion of the confessional singer-songwriter. With Mitchell's Blue, the genre reached its first epiphany.

"Blue was written and recorded at a time when I had no defenses," says Mitchell, and though her life's experience seemingly denies such naivete, the music makes the claim credible. "It was written at a time of purity and innocence, and nobody keeps that." Pause. "Not in this world."

The psychic tug of her early-'70s work remains a thirtysomething touchstone. "People approach me and tell me Blue calms their babies down," she says with a laugh. "At best it's an aspirin. That's what the work should be doing. The way it strikes and goes into the listener's life is the way the richness communicates itself."

If Joni Mitchell sometimes wore her romantic heart on her sleeve, it was always attached to a well-turned garment. "I was kind of an odd duck in that I always enjoyed fashion," she says of her coffee house days when "everybody dressed like they were in Castro's army."

By the time she got to Woodstock (actually, she never made it to the rock festival she celebrated in song), Mitchell was living with Graham Nash. The boyfriends who followed were once given an exhaustive family-tree treatment in Rolling Stone.

Mitchell still smarts from that and other public assaults. "It was coincidental that I would date an unknown musician," she says, "and he would suddenly become famous, frequently more so than me." The confessional mode, she discovered, exacted a price.

"Can you imagine what this job is like?" she asks. "When your work is dissected and pondered by the most ignorant and unimaginative of minds, there comes a time when you keep things to yourself out of necessity."

Mitchell, you might have guessed, has taken her share of critical shots. ''Here's what I think about critics," she says when asked if she was resentful. "The duty of the critic is to educate the ignorant, not to emulate them. What I don't like is the irresponsibility which I assume comes from being young, unattractive and underpaid." Ouch.

Mitchell's description of Mingus has some bearing on her own personality: ''He had a broad emotional spectrum, he cried easily, he fought easily, he got frightened like a child. He was incredibly pure and emotionally receptive because he lived such a wide spectrum of experience. He had an incredible jive-detector, and that's a tough thing to live with."

For Mitchell as well as Mingus, art was created in the name of pride. Just as the bass player would be irritated when the singer would change one of his notes, so the singer bridles at the static expectations that can be the unwieldy baggage of pop fame.

"I'm an idealist - it's obvious, isn't it? I'm an idealist in a world where inferior souls run things. We are facing extinction as a species because of it." The artist's only recourse, Mitchell believes, is to run free. "There was always a feeling that if you illuminate something, perhaps you could make things better. That's the work of poetry."

Joni Mitchell, poet and pop star, praised and panned, refuses to let her work aim for anything less.