Yaffe, who teaches at Syracuse, charts these encounters with a sure hand, and is a brilliant analyst of how Mitchell’s songs are made. But he leans a little heavily on quotations familiar to fans: many of his most revealing takes are culled from “Woman of Heart and Mind,” an excellent PBS “American Masters” documentary. He also seems to have let Mitchell get inside his head. In a strange preface, Yaffe describes interviewing Mitchell for a New York Timespiece in 2007, going to her house, and talking through the night, but getting “bitched out” by Mitchell once the piece was published. Then silence from “Joni” until years later, when, through a back channel, he’s taken back into her good graces. At times, his book feels as if its main objective were for him to never again be rebuffed by the “strong, resilient, defiant” woman he admires, who looked “more beautiful than she did in the ads for Yves St. Laurent that were in all the magazines.” Add Mitchell’s biographer to the list of men she played like a paddleball.

The frisson with his subject was perhaps inevitable. The collaborator in Mitchell always, in time, brings out the solo flier. It’s hard to think of a songwriter who has drawn so much from conversations but recorded so few duets. The pull of dialogue is countered by Mitchell’s strong solitariness, a tension that she works out in the lyrics of her songs. She sang with Chuck Mitchell early on, but they were “horribly unsuited” to each other as performers, and the aversion to sharing the stage with other singers was consistent throughout her career. On the live album “Miles of Aisles,” there is a spacious version of “You Turn Me On, I’m a Radio,” where a second, complementary voice appears to break in, weaving itself into the melody. Listen harder, though, and you realize that it’s a guitar, played to sound almost identical to Mitchell. It’s a commentary on her antipathy to others’ voices. The musicians she respects the most, Dylan and Leonard Cohen, are both notoriously limited singers, a fact that Mitchell reports frequently, and with evident joy.

Mitchell’s work often seems to be a repudiation of mere songwriting. Spoken stretches transfigure into melodies, which climb and play in the thermals; or her vocals gather steam only to break apart into stray phrases and verbal gestures. Her inspirations, she said, were the crooners of the pre-rock era, and Dylan, who could string lyrics together without the promise, or the threat, of an impending tune. (Dylan’s harmonica passages sometimes act as the only punctuation for his long musical sentences.) Mitchell had to make a new kind of song, in which conversation could flower, in mid-phrase, into music. Her tunes wander and veer; they manage their own beauty, bringing it forth at variable intervals. She wanted to create what she called “plateaus” for her lyrics, spans that she could prolong or cut short depending on the demands of her words and the emotional content that they ferried. In “A Case of You,” a song about Leonard Cohen, the lyrics turn on two reported fragments of speech. Both contain literary allusions; Mitchell was drawn to Cohen’s bookishness:

Just before our love got lost you said
I am as constant as a northern star and I said
Constantly in the darkness
Where’s that at?
If you want me I’ll be in the bar

“Constant as a northern star” is from Shakespeare’s “Julius Caesar,” but Mitchell’s retort wins the opening skirmish. Later, though, a line inspired by Rilke turns the tables:

I remember that time that you told me, you said
“Love is touching souls”
Surely you touched mine ’cause
Part of you pours out of me
In these lines from time to time

It is impossible to detect the duration of those phrases on the page, which is the point. When Mitchell started to play with jazz musicians, especially the bassist Jaco Pastorius, she would elongate the lyrics of her songs almost indefinitely, as she does on “Song for Sharon” or the title track of “Hejira.” One way of thinking about her turn to jazz, on “Don Juan’s Reckless Daughter” (1977) and on “Mingus” (1979), her collaboration with the bassist Charles Mingus, is that she needed longer and longer plateaus, stretching her lyrics over more even rhythmic surfaces. The only hint of a tune in “Coyote,” for example, comes with its minimal refrain, “You just picked up a hitcher / a prisoner of the white lines on the freeway”—phrases whose delivery relies entirely on factors localized within a given performance of the song.

The principle of delay works also with Mitchell’s rhymes, which are often the off-the-rack, Tin Pan Alley pairings that Dylan would adopt and, in songs like “Desolation Row,” deconstruct into prophetic nonsense. Mitchell does something different. Here is her take on “June” and “moon,” from the final track of “Hejira,” “Refuge of the Roads”:

In a highway service station
Over the month of June
Was a photograph of the earth
Taken coming back from the moon
And you couldn’t see a city
On that marbled bowling ball
Or a forest or a highway
Or me here least of all

The extra syllables building up to “moon” force you to take a longer than expected “road” to the destination. But the song’s exaggerated horizontality (coming at the end of a record about the highway) is neutralized by the cosmic scale that replaces it, which freezes everything in a single frame. It’s a painter’s way of resolving a set of dramas that are inherently narrative, as subject waits for verb, verse for refrain, lover for lover, coast for coast. As Yaffe points out, Mitchell learned from painting how to yoke “past, present, and future” together in one image.

Mitchell is now seventy-three. She hasn’t toured in more than a decade, and her health has been in steady decline for some time. In 2015, she had a brain aneurysm, and she suffers from Morgellons, a condition that causes the sensation of parasites crawling under and around one’s skin. She began chain-smoking when she was nine; the strong middle range of her voice, which allowed her to alternate so flexibly between high and low, was partly created by her habit. You could argue that it was also unmade by it—long ago, she began losing octaves, until her entire soprano range was depleted.

Still, it’s hard to think of a string of records as consistently powerful, shape-shifting, and durable as Mitchell’s albums from the seventies, beginning with “Ladies of the Canyon,” in 1970, and concluding, in 1979, with “Mingus.” These works are divided between fantasies of invisibility and flight, a teen-ager’s classic choice of superpowers. I was one myself when I plucked “Blue” out of a pile of albums in my aunt’s bedroom and played what seemed a distillation of the adult dilemmas I had been overhearing, throughout my childhood. This was Vermont in the seventies, and people everywhere discussed depth and superficiality, fate, luck, and the fluctuations of the moods, all in a vocabulary that Joni Mitchell had helped devise. Newlyweds were chilling out from the convulsions of the sixties. They had gone indoors, or joined the PTA. Tense and tragic Vietnam veterans opened shops full of glassware. The New Age was starting up, and meditation was practiced in church basements. It was the last moment in American pop when the modulations of ordinary existence were studied with any seriousness, and refined in songs that made family life meaningful and profound. It seems almost absurd to praise Mitchell for her ambience, when her songs are among the most stunning ever written. But the ambience comes back even now, very vividly, when you put those records on. You feel what Mitchell felt about Woodstock: the urge to get back to the garden, fully aware that it can’t be, that it’s impossible and faintly annoying to think otherwise, but knowing also that people’s best intentions are always beautiful.