It's five o'clock on a weekday afternoon, and the California sun is about to disappear into the Pacific Ocean, but Joni Mitchell — who happens to be known as one of the world's greatest and most original living singer/songwriters — is still wearing her pyjamas.

"I've got to go to a birthday party and wrap a present."

She is standing in the yellow-and-blue-tiled kitchen of her mansion in the upscale Bel Air neighbourhood of Los Angeles, where she has spent most of the day talking on the phone and drifting from room to room.

So far today she's been unable to get off the phone long enough to get dressed. The birthday party is for her former manager, Elliot Roberts, who is turning 60 (a milestone Mitchell herself will face next November).

Now she's on the phone again, doing an interview with some journalist in Toronto, once more telling the story of the tall girl with high cheekbones and long blonde hair who started her career in Yorkville coffee houses and became famous for turning her own psychic pain into popular art with such songs as "The Circle Game," "Chelsea Morning," "Woodstock," "Big Yellow Taxi" and "Turbulent Indigo," all the while recording 21 albums and winning five Grammy Awards.

To the despair of handlers trying to promote her current album, Travelogue, Mitchell almost never gives interviews, partly because she guards her privacy, partly because she thinks the media always want to turn everything into trivial gossip, partly because, as she explains bluntly: "I'm not good with the press. I can't handle it. I tend to be too honest."

But she has agreed to do just this one interview because it's about The Life And Times Of Joni Mitchell: A Woman Of Heart And Mind — a two-hour television biography that will premiere Tuesday.

CBC will show it in two parts this week and next on Life & Times. Then in April, PBS will show it in a two-hour slot in its prestigious American Masters series — a tremendous honour since the series does indeed focus on artists who truly are masters.

Having the film made was by no means an easy or relaxing experience but Mitchell has seen the finished product. She likes it and wants other people to see it, though she is also honest about her reservations: "You can't get a whole life into a bio. I feel that I'm a jukebox with 300 buttons, and people keep pressing only two — A1 and B2.

"The only reason I'm doing this interview is that I think the film is touching and unusual. I have my own criticisms of it, but it's good storytelling, and you get drawn into it. My father once said to me, `Joan, you've lived many lives in one.' I think this piece brings that out. It's like a fairy tale. It shows a life that's been wonderful and difficult and full of challenges and joys. Susan Lacy (the director and editor) took a lyrical, poetic approach; it's a very romantic piece."

In almost every room of Mitchell's house there is a radio tuned to a different station, though none is tuned to a music station. "There has been a tremendous drop in the standards of music on the radio. It was always the fluffy stuff that got the most attention, but there used to be places where the pioneering spirit had its place. Now it's all droning mediocrity. You'd have to be on ecstasy to enjoy the direction music has gone in. I've lost interest. I don't want to be a part of it."

Instead her radios are tuned to talk stations offering news flashes and political commentary, which all seem like madness to her.

"I wander through my house trying to get a picture of what is happening to the human psyche," she says in a tone that's both perplexed and angry. "The whole thing is ridiculous — a tragic comedy. We're marching into war. That means we've become an imperialist power, which goes against everything America stands for. It all comes down to personal economic interest."

Whatever her bank account may say, she is still essentially that vulnerable waif who was born in Fort Macleod, Alberta, raised in Saskatchewan, and who made the world take notice when she strummed her guitar and sang about her deepest feelings in a sweet soprano voice that ranges over several octaves.

Susan Lacy, the American Masters veteran producer-director, has gone way beyond the usual conventions of TV bios, creating a riveting narrative that tells the story of Mitchell's life while also providing a complex and intelligent overview of the ups and downs of her career. It includes not only marvellous performance footage but also revealing interviews with, among others, David Crosby, Graham Nash and David Geffen.

The film was produced by Eagle Vision, an independent company, in association with PBS, and has a different feel from most CBC Life & Times bios, partly because it's twice as long as most, and partly because it was acquired by CBC with little creative input.

For years Mitchell has bemoaned celebrity even though she was also conscious of enjoying its benefits, and she has always followed her own personal and artistic instincts rather than giving in to the fashion of the times and commercial pressures. You are not ever going to see Joni Mitchell in Las Vegas doing a "Joni's greatest hits" act that exploits her audience's nostalgia for the 1960s and 1970s.

Over the years she has faced her share of meltdowns. Husbands and lovers have come and gone. "I'm a serial monogamist and I've had good relationships," she says. "I'm proud that there are men in the bio who speak tenderly and insightfully about me."

The critics were sometimes unkind about her constant attempts to be fresh and inventive. She had a kind of nervous breakdown — out of which came fresh inspiration. She withdrew into painting and meditation.

She had already been written off as has-been a decade ago when she quipped: "Now I have rich people's problems, and you can't make songs out of rich people's problems."

That was before her spectacular 1994 comeback with an album that won two Grammys and new fans. Then in 1997, she was elected to the Rock and Roll Hall of Fame — the same year she was deluged with publicity about her reunion with the daughter she, as an unwed mother, had given up more than 30 years earlier.

Through it all, Joni Mitchell has never forgotten exactly who she is or where she came from. When you listen to her new version of "Both Sides Now" on her 2000 album of the same title, it's obvious her voice doesn't have the lyric purity it had when she first sang it three decades earlier. But now her voice has the rich and weary, smoky lived-in quality of a woman who has enough experience to understand at last the words she wrote so long ago.

"Something's lost but something's gained/ In living every day."

And when you hear the thrillingly mature Joni Mitchell revisit this signature song, you know you're getting the simple truth, without lipstick or makeup:

I've looked at life from both sides now
From win and lose and still somehow
It's life's illusions that I recall
I really don't know life at all.