JONI MITCHELL BLENDS VARIED MUSICAL STYLES FROM EVERY PHASE OF HER CAREER IN NIGHT RIDE HOME, A NEW ALBUM THAT JUST MIGHT BE HER MOST ACCOMPLISHED YET.

Twelve years ago, when Joni Mitchell was taking a drubbing for Don Juan's Reckless Daughter and Mingus, two wildly peculiar albums that were commonly regarded as the rash, overambitious work of an inept jazz wannabe, she told ) Rolling Stone that some of the things she'd done were half-baked, yes, but that "they lay the groundwork for further developments. Sooner or later," she insisted, "some of those experiments will come to fruition."

It's taken a while, but with her new album, night Ride Home (Geffen; all formats; 66), Joni Mitchell has proved herself right. From a musical standpoint, it's the most graceful record she's ever made; no awkward effects, no mad, darting tunes to accommodate mad, darting thoughts. The basic style is smooth, accessible jazz fusion, but there are so many echoes of her particular musical past-a wash of synthesized sound that recalls The Hissing of Summer Lawns (1975), the rhythmic quirkiness of recent albums like Dog Eat Dog, even a plain old circa 1970 acoustic guitar lick or two-that it simply sounds like the distilled essence of everything she's done before. Her lyrics are as elegantly lean as the music. Mitchell half-jokingly calls this album "a collection of middle-aged love songs," and though she doesn't appear to be any fonder of the aging process (she's 47) than the rest of us, her approach to the subject is tough, unsentimental, and blessedly free of the peevish whining that so often passes for middle-aged wisdom.

Of course, Joni Mitchell has never pretended to be wise; all she's really managed to deliver in the course of 16 albums is one of the most vivid and delicious chronicles of a woman's life that's ever been produced in any medium, anytime, anyplace. That's not something she gets credit for very often, in part because it's unseemly to treat a living and not-yet-venerable woman as if she were one of the Bronte sisters. But it's true, nonetheless: The "I" of Mitchell's songs is a half-real, half-fantasy character, which has evolved over time into a genuinely modern romantic heroine, a feminist devoid of cant, who's trying to figure out not how to live a politically correct autonomous life, but how to live a deeply fun autonomous life.

By now, people who've stayed with her over the years know the terrain of the Joni character almost as well as their own: the western Canadian town of her childhood and her hoodlum-y teenage pals; her travels, her troubles, her friends, her friends' troubles; the variously vain, smug, and actively evil strangers observed and dissected from behind a pair of sunglasses or a potted palm. And, of course, there's love, her favorite turf: from the fairy-tale imagery of "I Had a King" on her first album (1968) and the open wound of Blue (1971) to the sly and sexy fun of Court and Spark (1974) and Hejira (1976) to "Lucky Girl," her partly earnest, partly ironic tribute to wedded bliss on Dog Eat Dog (1985).

Mitchell's genius for illuminating what she feels, thinks, and sees has one stubborn flaw: She's never entirely stopped being the artsy girl, the classic middle-class, butterfly-painting adolescent, all unfettered creativity and ignorance of technique and mannered self-immersion, traces of which are to be found even in her best work. (The most egregious example of her self- absorption might be "Furry Sings the Blues" on Hejira, in which, contemplating how the blues were born, she sings: "W.C. Handy I'm rich and I'm fay/And I'm not familiar with what you played/But I get such stro-o-ong impressions of your hey day "-which, for sheer blithe condescension, is hard to beat.) That, more than anything, may be why people are reluctant to grant her the kind of legendary status accorded to '60s-generation prophets who've had far less to say than she-though it's hard to know what to think about a culture that's put off by a little artsy-girl preciousness while remaining riveted by the banal self-destructiveness and baby nonsense of classic artsy boys like Jim Morrison. Go figure.

The news is that the artsy girl seems finally to have been put to rest with Night Ride Home, and not a moment too soon: This album is about being a grown- up, dealing with standard mid-life concerns like trouble with your spouse ("Nothing Can Be Done," with music written by her husband, Larry Klein), getting religion ("Passion Play"), getting sued ("The Windfall"), and, almost as bad, the end of the world ("Slouching Toward Bethlehem"). Yes, that last song is a setting of W.B. Yeats' poem "The Second Coming," more or less: Mitchell has taken it upon herself to change the title and a good many of the words, presumably for reasons of relevance and musical flow, but the changes are nothing to get huffy about-her arrangement is so subdued and tasteful that the substance of the original poem comes through just fine.

Mitchell dips into her adolescence for two songs, "Cherokee Louise," a sad tribute to a sexually abused pal, and "Ray's Dad's Cadillac," a more cheerful take on the sexual customs of the '50s. As for present-tense love songs, there's "Night Ride Home," a perfect number about a perfect (shared) moment; melodically she hasn't done anything this straightforwardly pretty for something like 20 years. More interesting, though, is "Two Grey Rooms," about a woman who seems to have rented a flat just so she can catch an occasional glimpse of a man she's been in love with for 30 years: With its lush, string- soaked arrangement and cool, concentrated vocal delivery, it's vintage Joni Mitchell-crazy, elusive, gorgeous. This is an album with no splashy moments and no major statements; just musical refinement of the highest sort. For an artist whose publicity bio lists her vocations as "poet, painter, musician"-in that order-it's got to be a triumph. A