Roberta Joan Anderson was an athletic nine-year-old when the polio epidemic hit western Canada in 1952. By the time she got out of the hospital, her spine "looked like a freeway after an earthquake," and the muscles in her back and right leg were so withered that the doctors said she'd never walk again. The nine-year-old, however, had other plans.

"The fact of the matter is that I was, I am, crippled from it, but I just pretended like it wasn't there," says Anderson, who grew up to become Joni Mitchell, one of popular music's most significant singer-songwriters. "I got through my youth and my teens without any real problem - never missed a dance. I'm sure you can't say that all handicaps can be overcome by spirit," she adds, chain-smoking her third Camel of the interview, "but I really believe that a lot of them can."

Mitchell's indomitable "spirit" was called on to perform another near miracle last year, when, after a decade of low-to-moderate sales and quirky, avant-garde experimentalism, the singer decided to resurrect her career with an all-out, Big Business push, a la Tina Turner. Predictably, most of the record industry had about the same prognosis for her success as the long-ago doctors had for her dancing.

But Mitchell ignored industry doubts, the same way she'd discounted the effects of polio, and went on to produce "Dog Eat Dog," a beautifully crafted and intelligent appraisal of American culture in decline. Released toward the end of last year, the album had critics somewhat divided. Some put it on their "year's best" lists, while others, expecting perhaps her acoustic or jazz-pop formats of old, quarreled with its modern, synth-rock, audio-effect framework. Most reviewers, however, see it as a relentlessly inventive collage of sound, rhythm, and lyrics and an album that ranks with "Blue" and "Court and Spark" as a milestone in Mitchell's eighteen years of recording.

As a result, Mitchell, is doing something she's always refused to do, and that is to go out and personally hawk an album. In the flesh, she is something of a surprise. Her blond hair is no longer folkie-long and straight but medium-short and curly. Wearing a black beret, a black jumpsuit with purple stripes, and shoe, black, lace-up boots, she is both beatnik and brainy, charming and offbeat, with a strong Canadian accent. She is also quicksilvery - open, giddy, polite, even vulnerable one moment, and very, very cool the next as she stands with her arms folded, smoke-smoke-smoking that Camel and watching the video for Good Friends, her first single off "Dog Eat Dog."

The funny thing, she says, sipping black coffee at the Warner Brothers' Records office in New York, is that after all these years of invisibility she finds she loves talking to people, even the press - doing as many as ten interviews in a row on one banner day. "I'm in promo mode," she explains with a wide smile. "I want people to know the record is there."

With her first album, in 1968, twenty-five-year-old Joni Mitchell appeared to be a bell-bottomed folkie with a poetic eye and a sure knack for storytelling. Her songs grew musically more ambitious with each album, and her singing likewise grew confident and daring. By the time of "Blue" (released on the Reprise label in 1971), her fourth album, Mitchell had developed into a startlingly mature writer, fusing intensely intimate lyrics with emotional melodies in the contemporary folk tradition.

It was her fifth album, "Court and Spark" (1974), however, that really showed what she could do. No longer content to stay within the narrow confines of acoustic folk music, Mitchell ferreted out a complementary clutch of jazz-pop musicians (led by Tom Scott) who understood the unorthodox chords she employed in her open tunings on the guitar. Full of emotional rushes, romantic surges, and tight but well-paced music, "Court and Spark" (on Asylum) was a thrilling synthesis of rock, pop, and jazz, an album that assured Mitchell's position in the annals of popular music.

From her most widely hailed effort, however, Mitchell spiraled down with "The Hissing of Summer Lawns" (1975), in retrospect a brilliant album but ahead of its time. Universally drubbed for its use of polyrhythms, Burundi drums, modality, and unconventional song structure, the album began a commercial decline from which Mitchell is only now recovering.

"Hissing" was followed by "Hejira" (1976), a jazz-laced album of romantic introspection; "Don Juan's Reckless Daughter" (1977), a wandering collection of formless jazz; and "Mingus" (1979), a tribute to jazz great Charlie Mingus, which brought her scorn and ridicule from both jazz and pop circles.

Three years ago, Mitchell tried again, with "Wild Things Run Fast." The album won back some of the old fans with a pop, rock, and jazz orientation that was reminiscent of her early Seventies work. But if anyone thought she was about to repeat herself, they did not know Joni Mitchell very well. Her next album would take a 180 degree turn, from musings on love and romance to Mitchell's most overtly political statement yet.

"Dog Eat Dog" is an angry album, one that fairly seethes with outrage as Mitchell surveys the general state of things and finds rampant moral decay: government intervention in private lives, Yuppie materialism, Moral Majority censorship, Star Wars sensibility, and the frightening symbiosis of politics and religion. These subjects may seem light years away from Mitchell's best-loved work - confessional, highly personal songs of romance, self-obsession, and delusion - but in truth all of the new songs do have autobiographical roots.

The tone of the album comes from two experiences. The first involves an "unfair" California state tax levied in 1982 against Mitchell and nine other musicians who had artistic-control clauses in their recording contracts. The levy demanded 15 percent of Mitchell's income between 1972 and 1976 in back taxes. "Now I know firsthand what it is to be dealt an injustice by the government," says Mitchell, who has retained her Canadian citizenship. "I got my advance [on a new five-year Geffen recording contract], and the state of California said, 'Thank you very much. That's exactly what you owe us.' I'm telling you, it was like finding out that Daddy goes to hookers."

At about the same time, Mitchell married bassist Larry Klein (she was divorced from Detroit folk singer Chuck Mitchell in the late Sixties) and settled in for a "normal American year spending a lot of time at home, watching a lot of television." In fact, Mitchell says, she would have called the album "Songs of a Couch Potato" except for the seriousness of her message. Believing now that "the government is crooked," she was horrified at what she saw on her screen: an undeniable swing from the liberal, progressive Sixties and Seventies to a decade of right-wing conservatism and repression, best exemplified by the televised sermons of Jerry Falwell and Jimmy Swaggert. "The government," she concluded, "is now in league with the fundamentalists."

When it came time to record, however, Mitchell worried that the times were too superficial for such an album. "In a way," she said, "I don't blame people. It's a period of escape, like the early Fifties were, although for a different reason. Even the cause-mindedness, to me, has a more frivolous nature now than it did in the Sixties. I mean, with the causes this time you've got albums for them flashing on the screen," she says, laughing. "So on one level, it's just a great party time. Like my manager said, 'I don't know about these songs, Joan. Don't you have anything about sex and parties?"

Mitchell left her long-time manager, Elliot Roberts, toward the end of the project and signed with Peter Asher because Roberts was "too busy" with his enormous stable of clients. But she also admits that Roberts, concerned with her loss of power in the industry, pressured her to bring in a co-producer - something she had not had to do since her debut album.

In the end, British electronics wizard Thomas Dolby came in as a "color assistant," sharing producer's credit with Mitchell, Klein, and engineer Mike Shipley on all but three songs. The recording sessions, for the album lasted from February to September.

"This was one of the most difficult albums I ever had to make," she says, knitting her eyebrows. "I had never done any kind of work with a committee where, instead of just going with my natural enthusiasm for something, there were four strong opinions to consider - and a lot of opposition. But frequently, because of the delay and irritation, just like sand in an oyster, a pearl was born."

Some of the shiny, austere sounds on the album - the percussive whir of a cigarette machine on Smokin' (Empty, Try Another) or the street ambience of a burglar alarm on The Three Great Stimulants - have been criticized as "aural flash." But there is an appropriate uneasiness to this music, the effects lending the lyrics a power they would not have on their own. Better still, the electronics never diminish Mitchell or her material.

So far, with "Dog Eat Dog" selling well and bringing her back to center stage, the rest of Mitchell's life is on track too. "Marriage frees me up in a lot of ways. I feel mated," she says, pointing out that "Dog Eat Dog," for all its foreboding, is bookended by songs about friendship and love, a continuing source of optimism for her. "Relationship," she deems, "is everything."

Just the same, she says she still finds it difficult to express happiness in her music. "I'm a melancholy Nordic, you know. Midnight Sun in all the genes. Writing is very confronting work. A strong emotion - either a misunderstanding or a need to comprehend something within yourself-drives you to sit up all night to plums the depth of your being. It's only rewarding when the muse coughs up something that has the right sound, as well as confirmation and content. When that happens, or when you get lucky in the studio, man, there's not another job in the world you would want.

"Sometimes I start to feel that the gods are smiling," she says, sounding a lot like Roberta Joan Anderson from Saskatchewan. "To a certain degree I have to feel that there are forces at work beyond me."