Viewers in search of a momentary respite from the war should turn to KOPB (10) tonight to catch "American Masters" and its lovely portrait of Joni Mitchell.

"A Woman of Heart and Mind," written and directed by Susan Lacy, explores its knotty subject with incisive narration, sympathetic testimonials from friends, colleagues and lovers, and archival footage of the artist in performance and at home.

The 90-minute documentary presents a nuanced exploration of a musician whose genre-defying work altered the DNA of popular music on more than one occasion.

But of course, the joy her work inspired in others stood in contrast to the internal currents that led her to create it.

"(I wrote) to develop my own private world, and because I was disturbed," she says. "Bad fortune changed the course of my destiny. I became a musician."

Born Joan Anderson and raised by her grocery store manager and teacher parents on the Canadian prairie, Mitchell contracted polio when she was 9. While recovering, Mitchell honed her interests in poetry, music and painting. And once she was old enough, the teenage Mitchell would sneak out to the shady part of town to dance to rock 'n' roll.

Adventure had a price, however, which Mitchell discovered when her first sexual experience resulted in an unplanned pregnancy. Alone and penniless, Mitchell put her infant daughter in a foster home. Months later she married a fellow folk musician, Chuck Mitchell, thinking he would give her the financial and emotional support to raise the child.

Actually, he had no intention of caring for the girl, and she was put up for adoption. The loss would haunt Mitchell for the next three decades of her life.

After moving to Detroit, her husband tried to take an upper hand in their relationship, but Mitchell was far too independent to submit to his authority.

Mitchell honed her writing chops, then left her husband and moved to New York, where piercing, yet sweetly melodic songs such as "Both Sides Now" and "The Circle Game" earned her near-instant acclaim on the folk circuit.

"I couldn't believe there was anybody that good," says David Crosby, recalling the first night he saw her perform.

Film from the mid '60s shows Mitchell -- then in her early 20s -- as the very model of a willowy folk singer, her angular face framed by curtains of strawberry blond hair. But her fragile look belied a creative will that could topple mountains. A late '60s love affair with fellow musician Graham Nash fell apart largely because of their competing creative impulses.

"It was an intense time of, 'Who's gonna get to the piano first, who's gonna fill up the space with their music first,' " he recalls.

Fearing the relationship might threaten her work, Mitchell broke off their engagement and ventured to Europe. There, she wrote the bulk of "Blue," an album whose intensely personal songs served as a signpost for a generation and for the next generation of singer-songwriters.

Always attracted to the melodic possibilities of jazz, Mitchell drafted a group of like-minded musicians to open up her sound. The first product of this idea, 1974's "Court and Spark," which included "Help Me" and "Raised on Robbery," became her biggest hit. Subsequent records explored the wilder frontiers of jazz.

While she never really lost her audience or overarching acclaim, in the '80s and '90s Mitchell's face seemed to harden around her ever-present cigarette. Her work (sample title: "Sex Kills") fixated on the most anguished sort of pain and injustice.

Still, the film seems to shade its eyes from Mitchell's less appealing side: Her bouts of sanctimony, her feuds with certain magazines, a sense of humility Crosby once compared to Mussolini's. But there's a reason for Lacy's sympathy.

As she had written about repeatedly, if elliptically, in her songs, much of her internal reality had been shaped by the absence of the daughter she had surrendered in the mid-'60s and never heard from again. Mitchell made a public appeal to find the girl in the mid-'90s, and the two were eventually reunited.

The documentary's final scenes show a radiant Mitchell frolicking with her daughter and grandchildren, and Lacy's film may be just another flower in a bouquet of late-career plaudits. But as the documentary makes clear, it's the glowing faces on Mitchell and her newfound family that are her true reward.

Peter Ames Carlin: 503-221-8562; petercarlin@news.oregonian.com