Joni Mitchell may not have actually started the singer-songwriter phenomenon, but she sure as hell moved the genre centre stage. In terms of the "confessional" nature of the Lyrics, and the use of language that is so precise and so poetic there isn't room for a wasted syllable, her 1971 album Blue was a watershed.

"The emphasis on lyrics, I think, began with Dylan" she suggests. "That's where I picked up the gauntlet. I always wrote poetry, but I never liked poetry! I only wrote it when I was emotionally disturbed. Like, when a friend of mine in high school committed suicide. Or something like that. There were things that would make me go home and write. And then I'd put it in a drawer and, sometimes, when I had to turn them into English class, I would. And it was recognised, in High School, that I was a writer. But I never based my identity in that. Besides, I liked to dance! So, for a dancer, the Lyrics didn't really matter. 'Tutti Frutti' was fine by me" Joni admits that when Bob Dylan first arrived on the scene she was not impressed! Mostly because he seemed, to her, like little more than a copycat of Woody Guthrie.

"I have this need for originality," she explains. "It's actually in my stars. I was born on the Day of the Discoverer and that, I believe, had a profound influence on this need to be original. And also, because I've always been a painter, there is the painter's need to discover a new voice. Whereas musicians go into a tradition, with no need for discovery. But there came a point when I heard a Dylan song called Positively Fourth Street and I thought 'oh my God, you can write about anything in songs'. it was like a revelation to me."

For his part, Dylan apparently first realised "you can write about anything in songs" when he heard similarly caustic lyrics by Hank Williams, such as 'Can You Please Make up Your Mind?' One presumes that Joni Mitchell, born in Saskatchewan, Canada in 1943 and raised listening to Williams, also noticed the same tendencies in his songs?

"I grew up listening to country music but I didn't like country music," she says, laughing. "Yet I liked Hank Williams even so, the things I liked didn't have the kind of the depth you're talking about. I listened to 'Honky Tonk Blues'. Stuff like that. And liked them simply because they had a certain frivolity to them, which, as with early rock n' roll was fine by me. I was as I say, a dancer. Music was just for having fun!"

But it could also be argued that music was a form of spiritual healing for Joni Mitchell. In his recently published "unofficial" biography, Both Sides Now, Brian Hinton argues that Joni's desire to dance was strengthened rather than weakened in 1952, when she was diagnosed as having polio. It was a traumatic experience. Not only did she endure the horrors of a 'treatment' that involved scalding flannel rags being placed on her bare legs then quickly ripped away - thus blistering her skin - but the nine-year-old child was actually told that she would probably never walk again. Joni Mitchell, exhibiting the sense of fierce determination that has marked her every move ever since insisted she would walk. And, as sceptical nuns wheeled her towards a ramp with long railings and left her to try make that arduous walk on her own, she was focusing on just one thought: "If the disease spreads to your lungs you are doomed to spend the rest of your life reclining in an iron lung with your head sticking out. I can hear the iron lung wheezing in the background."

Joni not only made it, unaided, to the end of that ramp. During her year of recuperation at home, she defied her illness even further by deciding to become, not merely a dancer, or any dancer, but what Bobby Darin would describe as the 'Queen of The Hop.' To capture this crown she practised on a daily basis, using, as her partner, the handle of her bedroom door. Joni made it to the end of that particular "ramp" too and was soon seen swirling her way around rock 'n' roll dance floors in downtown Alberta - a period of her life she celebrates in the song 'In France They Kiss on Main Street.'

Brian Hinton also suggests that it was during her stay in hospital that Joni discovered the joys of painting. Having been told she wouldn't be going home for the Christmas holidays, someone gave her what she'd later describe as "a colouring book with pictures of old fashioned English carollers and Lyrics to Christmas carols." The young Joni not only turned those white spaces into a kaleidoscope of colours but "let rip" with those carols as loudly as she could, "So all the other kids could hear."

In other words, you don't have to be Einstein to realise that art was a balm to Joni Mitchell's soul from the start. And so it remains.

"The first music that inspired me to make music was a piece by Rachmaninoff 'Variation's On A Theme By Paganini,'" Joni recalls. "It was one of the most beautiful melodies I ever heard. Very sad, very romantic. I was seven or eight and I went to see a Kirk Douglas movie, with a friend of mine who was a piano genius and he could play that piece, so I wanted to learn to play piano. But piano lessons, once I got into them, were painful! They used to hit you with the ruler, while you were learning the scales. But I just wanted to get, as fast as possible, the ability to play that piece of music! So I quit piano lessons. And the love of creating music went underground. But that piece of music really was a big push for me. So when I began to write my own songs they had that sad, romantic, quality. Simply because Rachmaninoff was the first thing I loved."

From Rachmaninoff to rock 'n' roll? Why not? Indeed, Joni's earlier reference to 'Tutti Frutti' also reminds us that she did come of age during the birth of rock 'n' roll.

"Well, I absorbed a lot of rock 'n' roll before I got into folk music, which is something, I think, people tend to forget," she points out. Especially those who want to pigeonhole me as a folk singer which is something I really haven't been since about 1964. In fact, when I started recording, in 1967, it was more folk-rock I was doing."

At High School, she was into the likes of Miles Davis as well as Lambert, Hendricks and Ross. The latter were, she says, "my Beatles and theirs was the record I wore thin, the one I knew all the words to." The record to which she's referring is Hottest Sounds in Jazz, a post bebop collection that included 'Centrepiece', a song seamlessly stitched onto her own composition 'Harry's Game', for her album The Hissing of The Summer Lawns. Mitchell also recorded the Ross and Grey tune 'Twisted' for Court And Spark. "So what you've got is a lot of different musical threads that have to be synthesised over time," she explains, adding that when she left High School and started singing in folk clubs the music came from what she calls an "Anglo-melodic" base.

"When I came into music, professionally, in the beginning, the sound in the coffee houses of the day was definitely Irish influenced," she elaborates. "As in, British Isle ballads, very melodic, in a minor key."

And as with Rachmaninoff, very sad? "Definitely like many of the songs on the Chieftains album, Tears of Stone. In fact, I started out singing that kind of song but, as a performer in clubs, I felt I needed some levity, so I started spinning yarns on stage. But then I met this Englishman named Peter Ebbling, who cut half of my repertoire back! He said 'you can't sing this, this or this because this is my territory!' So you were almost forced into writing in that genre. Because no matter where you went you had somebody saying 'you can't play that here, it's my song.' And I admit that the first songs I wrote were not very soul-searching. They were very young. Lines like 'night in the city looks pretty to me.' Although I did write 'Both Sides Now' as one of those first ten songs. But that is half naive and half worldly. Each verse alternates in that way."

Elaborating on the genesis of one of her most famous songs Joni explains that its roots also stem, in part, from a fairy tale she was writing. "It was called Mythology, and focused on a place that had two kingdoms. It was kind of like childhood Zen. The kingdom of Fanta and the kingdom of Real. Fantasy, reality. And 'Both Sides Now' came out of that mythology, from Siquomb, the queen of that mythology. It was a children's story! And yet people say it's narcissistic because I'm referring to myself. But it was the queen of the kingdom of Fanta singing. And the whole idea probably came from my reading Lord of The Rings. That was a direct influence."

Shifting focus back to Blue, Joni claims that from that album onwards she became "a scribe, a witness" of life. "Basically because I had this craft now and I was looking for subject matter, things to write about that I felt were pertinent," she says. "And I saw tremendous social struggle all around me. And saw things into the future. I do have that tendency to look ahead. And I didn't really fit with my generation, either. I really felt I was an 'odd duck' within the context of my own generation."

Does Joni still feel that way? Spiritually dislocated? "I don't feel dislocated, in my personal life, I have wonderful friends," she responds. "But as for spiritually? To tell you the truth, I haven't really done the disciplines that would make me feel centred all the time. Partly because I never found a religious orthodoxy I could believe in. But I don't feel buffeted around like I used to. I'm much more grounded now." Indeed, Joni recently said, "think of me as a Catholic priest that drinks a little with the Dockers!"

"That was for my mother's benefit," she says, laughing. "Because my mother said I was immoral after one writer blamed me for single-handedly destroying the family unit in America. But then my mother has always been critical of things like unmarried sex. Even to this day she is."

"But as for my own religious base, I am a student of comparative religions. I like bits and pieces of all of it. I've got a shrine in my yard. It's a Spanish house with a Madonna. My house-keeper is a Catholic and we drop to our knees a couple of times out there."

Nevertheless, in her song 'The Same Situation' Joni, reinterpreting Nietzche's God-is-dead dictum, does refer to the Lord being "on death row." Likewise, Joni's lines such as 'acid, booze and ass/needles, guns and grass' capture to perfection at least some of the alternatives to religion many people, including Joni herself, have tried since, uh, God died.

"That's why I like Nietzche so much," she says. "But I think Nietzche is misunderstood. I think the main thrust of his thinking - and Carl Jung's - is that the church had really taken the blood out of Europe. It had everybody cowed. Nietzche was not a critic of Buddhism because there is a lot of joy in Buddhism. But he was a critic of the influence of the churches on Europe. There's a great scene in that Spielberg movie about slavery. Remember where you have all these black slaves in chains and there comes this Christian choir, with their hymnals? And they're singing then one of the slaves says to the other 'are they sick?' (laughs)

Joni Mitchell suddenly becomes more contemplative. "But, seriously, I have felt the sting of religious hypocrisy. I was sick a lot, as a child. In Catholic hospitals. Yet, on the other hand, a Sister Mary Louise, once said to me 'you're exactly what I need'. She thought I was like a Thomas Merton, tried to get me to convert to Catholicism, thought I was divinely inspired until my work got quite carnal. But before that happened, I did play at Nuns' conventions for her and she really believed I had, as I say, some kind of divine spark."

Reflecting further on that "acid, booze and ass/needles guns and grass" line, does Joni understand why more and more people these days might turn to drugs for a "high", fearing that all true spirituality has gone from contemporary society?

"I understand," she says, softly. "I've never done junk but it is a kind of velvet blanket that has this internal comfort. Yet, better not to start. What if you liked it?"

Some jazz musicians say it is the only way they knew to "kiss God." "Well, it worked for Charlie Parker but what other saxophone player did it work for?" counters Joni. "And even he died as a relatively young man, in a 70-year-old body. There is that defiling of the temple, in Buddhist terms. And that seems like the coward's route to me."

Joni Mitchell could hardly be described as a "coward." Indeed, looking back on Blue she once said it was probably the purest emotional record she'd ever make.

"In order to survive in the world, you've got to have defences and mine just went," she explained. "Actually, it was a great spiritual opportunity but nobody around me knew what was happening. All I knew is that everything became kind of transparent. I could see through myself so clearly. And I saw others so clearly that I couldn't be around people. I heard every bit of artifice in a voice. Maybe it was brought on by nervous exhaustion. Whatever brought it on, it was a different un-drug-induced consciousness. In order to make that album we had to lock the doors in the studio. Only (engineer) Henry Lewy and I were in there. When the guy from the union came to the studio to take his dues I couldn't look at him. I'd burst into tears. I was so thin-skinned. Just all nerve endings. As a result there was no capacity to fake. I'll never be that way again. And I'll never make an album like that again."

Looking back on that quote now, Joni Mitchell finally reveals why she was so fragile at the time. "All those songs I wrote the way I did because I had to," she explains. "I was emotionally disturbed, again, which brings out the poet in me. I had some hard life changes handed to me. The story is out on the streets now, but what happened was that I had to give up my daughter for adoption. Because of poverty. Not having the money to feed and clothe her and put a roof over her head."

Kilauren is the daughter Joni was singing about in 'Little Green' from Blue. "The time of her birth really was traumatic for me," Joni continues. "That's why I could identify with the women who were sent to Magdelene Laundries in Ireland, which I wrote about in that song for Turbulent Indigo." "But, to get back to why I wrote those songs on Blue, the point is that soon after I'd given up my daughter for adoption I had a house and a car and I had the means and I'd become a public figure. The combination of those situations did not sit well. So I kind of withdrew from music and began to go inside. And question who I was. And out of that, Blue evolved. I guess I was being a 'shrink' to myself! And if I, in the process of doing that, found something I thought was universal I was willing to open up at that level."

Joni Mitchell pauses. But only to take a drag from one of her seemingly ever present cigarettes. "There wasn't much illumination in psychology books at that time. I'm not sure there is now," she continues. "There was a lot of pigeon-holing and labelling, nothing very useful if you were really thinking. There didn't seem to be anything good to hang onto. Even the good books. And believe me, I searched through a lot of them. Dao-ism, what-ever. I became a seeker. I also was contemptuous of the kind of pseudo-spirituality afoot at that time which I found unsettling. So the point was that if I was to discover any illumination, it had to be backed up in the character of someone. I wasn't setting myself up as any sort of guru! But if I was to find a revelation, I felt it was more honest to present it, with a character, which I was drawing off myself. A character that was vulnerable and lost."

Which is why Blue, in terms of its lyrical content, was more personal than Joni's three previous albums, Joni Mitchell, Clouds and Ladies of The Canyon. And, true to her word, she never did make an album quite as raw or revealing again.

Read Pat Carty's reflections on Blue at 50 here.