This article originally appeared in the first edition of the Ultimate Music Guide published on May 19, 2017.

Joni's third album overflows with remarkable images - "The thirty-third floor in the air"; "With your father's gun alone"; "The face of the conquered moon" - but one looms over all the others. It is the line in "Woodstock" that describes jet bombers "turning into butterflies above our nation". Rarely has both the terror and the idealism of the late 1960s been so powerfully wrought, the competing forces of the times so perfectly evoked. The image spoke to a nation and a generation, but it also holds a metaphorical significance for the 26-year-old woman who wrote and sang it. Ladies Of The Canyon is the sound of Mitchell cracking out of her chrysalis and starting to soar.

With Clouds, Mitchell had forged a productive niche. She was by now a rising star, firm friends with James Taylor, Carole King and the rest of that golden set forever associated with boom time in laid-back Laurel Canyon. She could easily have followed many of her contemporaries in pursuing that distinctive sound and sensibility for the foreseeable future. Instead, she was gripped by a restless urge to change and move forward. She talked about wanting her records to become more complex, more sophisticated, for them to draw from a wider palette of colours. Implicit in this was a clear desire to let the music, rather than just her voice and her words, carry a greater weight of meaning. She was not content to allow her work to be merely pretty or simply clever. It had to have guts, too.

Ladies Of The Canyon is, mostly, the record on which Mitchell delivers on all of those ambitions, although in some ways it remains a transitional album. While more decorated than Clouds, it is still relatively sparse- half the tracks feature just Mitchell's voice with her own solo instrumental accompaniment. Strings, additional vocals and horns are subtly deployed, but as a rough rule of thumb, it's whenever she chooses the piano as her primary conduit of expression that things start to get really interesting. The way her voice colludes with the instrument brings out astonishing new tonal shades, while her increased proficiency offers not just an increased range of textures, but a new way into her music. On songs such as "Willy", her love-struck hymn to Graham Nash, the music follows the whims of the heart. It ebbs and flows, with its own internal logic, unbound by any formal structure, her accompaniment subtly changing with each new line.

On "For Free", the rippling piano captures the wistfulness of a song which contrasts the experiences of a successful professional musician who "plays for fortunes", and the "one-man band by the quick lunch stand", busking on the street comer purely for the love of it. It's a gentle song of disquiet, dispatched from the cusp of fame, half-observed, half-experienced, posing the question: what happens to the soul when your passion becomes a commercial transaction? Mitchell had plenty of reasons to ponder such matters following the release of Ladies Of The Canyon, as it dominated FM radio throughout the remainder of 1970, and quickly went gold. Her response was to take a prolonged break to consider her options. The melody is rich and beautiful, the contours teased out by a cello buried low in the mix, and the free-spirited horn that appears on the coda, an auteur touch echoing the sound of the street musician in the song, and an early signpost towards her coming infatuation with jazz.

A much more profound sense of materialistic disgust hangs over "The Arrangement", which feels like a direct forerunner of Blue in its mood of elegant desolation. It's a tale of emptiness and unfulfilled promise, the catalogue of consumerist trinkets no match for some interminable void: "A credit card/ Swimming pool in the backyard ... racing cars, whiskey bars/No-one really cares who you are". Her voice swoops from soprano to husky whisper, repeating a central refrain - "You could have been more than a name on the door" - which enforces the sense of an impending existential reckoning.

It is one of two tracks on Ladies Of The Canyon that point directly towards the future. The other is "Rainy Night House", which shares its pervasive sense of unease. It's an intricately detailed memory of a night spent in the family home of a man born into wealth, who desires to renounce his privileges in the quest for some greater meaning. Indicative of Mitchell's newfound ability to achieve a lot with just a little extra production flair, it's a brilliantly arranged piece: a lowering cello weaves its way through the piano, while the vocal flourish that follows the line about "the upstairs choir" - as well as the hair-raising keening sound that brings the song to a close - are masterly touches.

Here, the confessional side of her writing, soon to fully bloom on Blue, starts to become a public drama. Already critics and listeners were beginning to speculate about the personalities involved. At the time, Mitchell was going out with Graham Nash, a relationship that would prove mutually productive. In "Conversation", Mitchell is the other woman in a three ringed romantic circus involving a musician (perhaps it is Nash; perhaps not). She recalls their idyllic stolen moments- "I bring him apples and cheeses, he brings me songs to play" - while casting barbs at her rival who "speaks in sorry sentences ... and only brings him out to show her friends". The song bounces along on a lively, openhearted rhythm-guitar figure and her stunning vibrato, creating an outer brightness that belies an inner darkness. The faux-naif "doo-doo-do"s, fluttering saxophone and flute that appear at the end are applied with a kind of exuberant innocence. There is a joy in hearing Mitchell beginning to explore how these particular colours should be painted into her music.

"Willy" is definitely for and about Nash (his middle name is William), "my child ... my father". Another undulatin gpiano piece, perfectly formed, it's a lovely song of romantic rapture and regret. "I feel like I'm just being born", she sings, and she sounds it. By the summer's end, the relationship would be over, although much affection remained on both sides, and Nash would continue to infiltrate her songwriting.

There are times when Ladies Of The Canyon goes so deep it becomes almost daunting to follow. The mysterious "Blue Boy" is a sad, strange and highly stylised tale of the impossibility of love, while "The Priest" is dense with a heavy symbolism. Mitchell picks out a John Fahey-like acoustic blues figure in a minor key, and there are echoes too of the early work of another former lover, Leonard Cohen, in the song's druggy undertow and its thick waves of imagery.

After all that introspection, Mitchell tilts her head back to gaze at the wider world. "Big Yellow Taxi" might take its title from the means of transportation preferred by a departing lover, but its concerns are weighted more towards the universal than the personal. Written following a dispiriting visit to Hawaii in November 1969, its message of ecological doom is simple - "They paved paradise ,put up a parking lot" -and the medium irresistibly direct. Driven by the same fantastic rhythm-guitar sound as "Conversation", as big and wide as a Cadillac, "Big Yellow Taxi" lends Ladies Of The Canyon a welcome shot of levity. Running to barely two minutes, it's offhand in the best possible sense. With its silly octave leap and self-conscious laugh, zinging harmonies and pop melody, it gave Mitchell her first hit single as a performer, reaching No11 in the UK and No67 in the US.

"Woodstock", on the other hand, expands Mitchell's earthly concerns to the level of collective cosmic consciousness. Inspired by the vast gathering of humanity that descended on Max Yasgur's farm in mid-August 1969 for a festival she neither performed at nor attended, but instead watched on television from her hotel room, Mitchell unleashed a series of lines and images as unforgettable as those in Bob Dylan's "A Hard Rain's A-Gonna Fall". With its references to the "garden" of Eden, to "a child of God", and a mass of people "half a million strong" embarking on a pilgrimage, "Woodstock" offers the possibility of a reclaimed paradise where "we are stardust, we are golden". Perhaps only someone who wasn't stuck in that very earthbound mass of muddy humanity could have brought such gravitas and generosity to the concept underpinning the song. Mitchell's great achievement here is to make it sound awe-inspiring rather than ridiculous.

The stinging blues-rock version of "Woodstock", recorded by CSNY for Deja Vu and released as a single at the same time as Ladies Of The Canyon came out, was pitched directly as a rousing generational anthem. Mitchell turns her own composition into something less celebratory, more elegiac. Picked out with thick, sticky notes on the electric piano, it dispenses with the optimism of CSNY's cover in favour of a slow-burning hymn, setting a glimpse of bliss against the churning nature of the times. Mitchell's voice is stripped of any coffee-shop folk sweetness, preferring instead an uninhibited soulfulness, most affecting during the scatting at the song's conclusion.

While Mitchell spends most of her time on Ladies Of The Canyon casting a line into deep, dark waters, a handful of tracks are content to paddle in more familiar streams. Revisiting the upstanding folk of her previous work, "Morning Morgantown" is almost indecently pretty, a storybook portrait of idealised smalltown life. All bright smiles, "coloured rings" and "tea and lemonade", it's not quite the sole occasion on which the album veers towards tweeness. Already recorded by Buffy Sainte-Marie and Tom Rush, "The Circle Game" traces the cycle of life, as a young boy becomes a man. Time is a carousel of "painted ponies", and the world promises "dragonflies", "cartwheels" and "falling stars". "The Circle Game" provides the album with a satisfyingly upbeat singalong ending, but its well-ordered craft and sweetness have more in common with what has come before than what lies ahead.

Likewise, the rather prim title track finds Mitchell at her most austere and her voice at its most bell-like, as though in conscious imitation ofJoan Baez. Introducing us to the titular ladies of Laurel Canyon - Trina, Annie and Estrella - she celebrates a wellspring of female creativity that manifests itself in a variety of forms. Whether making clothes, baking brownies, singing songs or rearing cats and children, they are all "pouring sunshine down the canyon". It's a well-meaning portrait of sisterhood and arty Los Angeles life that- if it didn't already- would soon sound like a parody.

Such moments of prettiness risk appearing rather tame next to the riches on offer elsewhere on one of Mitchell's landmark albums, but the contrast between the light and the shade ultimately makes for a beautifully rounded record. And in any case, these sugary songs provide us with a kind of farewell. She would rarely, if ever, sound so relatively uncomplicated, so sunny, again.