Five years ago, Joni Mitchell announced her retirement from a music business she'd labeled "a cesspool." Who could blame her?

The type of art Mitchell has spent most of her 64 years pursuing and perfecting is not exactly in vogue. It's a smart blend of introspective poetry first married to folk and, later, to a groundbreaking hybrid based on jazz harmony and often featuring some of the best players jazz has ever coughed up.

Record labels don't really know what to do with a songwriter and performer as stubbornly unique and consistently challenging as Mitchell. Radio? Forget it. It's over.

So why should Mitchell bother? It's wholly reasonable to suggest that she is way too good for the marketplace.

Fittingly, it wasn't some desire to reclaim a commercial presence that brought Mitchell away from her painting easel and back to the recording studio. It was, rather, disgust. "Shine," Mitchell's first album for the Hear Music label that had considerable success earlier this year with Paul McCartney's "Memory Almost Full" platter, is centered around the artist's reflections on war and ecological disaster.

It's as profoundly beautiful an album as she has ever made, and anyone who's been paying attention over the past four decades knows that this is a considerable claim. At turns hopeful and tinged by a deep remorse, "Shine" is harmonically sophisticated music that can claim only a tangential relationship with what we now consider pop. Most of the performances on the record are Mitchell's alone, although some well-chosen guests - most notably, saxophonist Bob Sheppard, whose plaintive sax playing contributes stirring counterpoint to Mitchell's jazzbased phrasing - add depth to the proceedings.

"Holy war/genocide, suicide, hate and cruelty/How can this be holy?/If I had a heart, I'd cry," sings Mitchell on the album's third song, thereby explaining to us her reasons for picking up a guitar again. This is not exactly misty-eyed, "Days of Wine and Roses" stuff, but despite the dour topicality of "If I Had a Heart," Mitchell is able to convey a stoicism that is touching in its consistency.

"This Place," which positively soars on a buoyant melody, interjected by Sheppard's heartrending soprano sax stabs, suggests our race lacks the grace to save itself. "Money, money, money/Money makes the trees fall down/It turns mountains into molehills/Big money kicks the wide wide world around," she sings, contradicting the tune's sunny chordal disposition in a striking manner.

This is just the sort of stuff that right-wingers point to when they decry the doe-eyed "simplicity" of "the liberal world view," and Mitchell knows that well. Defiant as ever, she leans heavily on the intractable logic of her lyrics as armor against a world she clearly finds both hostile and bitterly disappointing, at least where men are concerned. (Nature, as has long been the case in Mitchell's songs, is not so much idealized as celebrated throughout "Shine"). Obviously, this will hold more appeal for listeners who agree with Mitchell than it does for others. I doubt this will bother her.

Musically, "Shine" splits the difference between the sparse beauty of "Night Ride Home" and the more ornate work arranger Vince Mendoza offered Mitchell's songs on the transcendent "Both Sides Now." (A real orchestra would've made these songs even stronger, but as it stands, Mitchell has done a wonderful job orchestrating this album herself, via her piano, synth and guitar playing.)

The record opens with the inspired jazz harmony of the instrumental "One Week Last Summer," a soulful mixture of piano, synth strings, orchestral sounds and Sheppard's languid alto sax. Mitchell digs deep into jazz balladry for the album's saddest moments - the twilit rumination "Bad Dreams," the despairing elegy "Strong and Wrong" - and balances their yearning with more folk-based pieces that provide relative levity. In so doing, she achieves a masterful balance, something difficult to achieve with subject matter this heavy.

The centerpiece of the album is the title track, which is hard to interpret as anything other than a farewell from Mitchell, who lets the piece unfold with a gorgeous near-ennui, like a secret prayer for a world unaware of the massive mess it's in. Mitchell recounts all she's seen through a compassionate lens, contrasting the beautiful with the unbearably ugly in a voice touched by a weary (and wary) optimism.

Here, Mitchell sounds like she's singing over the closing credits of the film of her career. If so, she's going out with all the grace she's brought to her peerless body of work throughout these many years. If this is the end of it, than we're lucky we had her for the time we did.

**** (Out of four)