There are few holy grails left in music. The internet has made previously hard-to-track-down items like Prince's Black Album (pulled from stores in 1987; bootlegged forever and recently made available legally through Tidal) or Stevie Nicks and Lindsey Buckingham's pre–Fleetwood Mac 1973 album Buckingham Nicks (long out of print on vinyl, never pressed to CD) available at the touch of a button. So hearing the mythical Columbia studio demos documenting the collaboration of Betty Davis and her then-husband Miles from 1968 to 1969 is like discovering an Archaeopteryx. We hear how two titanic musical and artistic forces intersect, and how it affected the work that came in the wake of their union.

Betty Davis's influence on her ex-husband's work is well-documented. A surrealist photograph of Betty’s face by photographer Yasuhiro “Hiro” Wakabayashi appeared on the cover of Filles de Kilimanjaro in 1968, and the song “Mademoiselle Mabry (Miss Mabry)” is a lush tribute to her charms. Filles de Kilimanjaro marked the start of Miles’s new experimental phase — as he fell in love with Betty Mabry, his music opened up even wider than before. In a Silent Way continues the expansion of Davis’s sound into the new frontiers of his electric period. Many contemporary rock and jazz critics at the time condemned the crossover, missing the point. Rather than continue in a vacuum and become trad jazz, Miles responded to what was happening around him as the '60s progressed, musically and politically — and his channel into that countercultural New York world was his new wife Betty Davis. That his late '60s creative rebirth coincided with his relationship with Betty Davis was not a coincidence. She embodied the '60s archetype of the Liberated Woman — the woman who seizes her destiny as a creative and sexual being.

Betty Davis allegedly inspired (and possibly also named) Miles’s landmark 1970 double album Bitches Brew. He was 41 when he met 22-year-old songwriter and model Betty Mabry, who had written “Uptown” for psychedelic funk-rock pioneers The Chambers Brothers. Betty introduced Miles to the music of Sly Stone and Jimi Hendrix, also encouraging his move toward jazz fusion, as well as psychedelic music and ideas. The Columbia Years 1968–1969, released this month by the Seattle reissue label Light in the Attic, makes it clear what a presence Betty Davis was. Miles described her in his autobiography with awe, calling her “a big influence on my personal life as well as my musical life” and “talented as a motherfucker.” She took Miles electric because she is, herself, electricity.

Mabry grew up in Pennsylvania and North Carolina and moved to New York at 16, working as a model while attending FIT. She lived in Greenwich Village and mingled with the folk and psych-rock crowds, a known charismatic beauty. In the '70s, she wore skimpy stage outfits and freely expressed herself sexually, with songs like “He Was a Big Freak” — an ode rumored to be about either Miles or Jimi Hendrix, but more important as the ribald anthem of a woman controlling the stakes of her own pleasure. Betty's '70s albums were boycotted for their explicit content, but it certainly didn’t help matters that RCA didn’t know how to promote her properly. Her work anticipated genre-blending artists like Erykah Badu and Prince and the unapologetic sexuality of '80s Madonna and Janet Jackson, and places her alongside Patti Labelle and P-Funk in terms of intergalactic, life-affirming, and funky celebrations of blackness.

Davis's albums were collectors-only until Light in the Attic's 2007 series of rereleases, which spurred an overdue consideration of her work. Davis’s legacy has not only grown but changed, as critics and fans have finally been able to recognize her greatness not just as a muse, but as a pioneer herself. The Columbia Years places Davis with some of Miles’s crew — she puts Wayne Shorter and Herbie Hancock through their paces as she rips it up on each track. There are snippets of conversations between the Davises, with Miles advising Betty to keep chewing her gum while she sings to sound properly casual.

The Columbia Years are produced by Miles Davis and his right-hand-man, Teo Macero. With a backing band that includes drummer Mitch Mitchell from The Jimi Hendrix Experience, Hancock on keyboards, bassist Harvey Brooks, Wayne Shorter, Hugh Masekela, and members of The Crusaders, it feels like The Basement Tapes for jazz-rock nerds. “Hangin' Out” sounds like the direct point that leads to Miles's 1972 On the Corner and Corky McCoy's iconic cover art.

Interpreting two different songs written by white men fantasizing about being black Delta blues musicians — her British friends Cream's “Politician” and Creedence Clearwater Revival's “Born on the Bayou” (of Northern California) — Davis refills them with fresh, cold milk and makes you reconsider the originals in new ways. She takes the South-fetishizing styles of both songs and digs all the way in until she gets to the real dirt, a year before Tina and Ike Turner's cover of “Proud Mary.” When she sings “Hey now, baby, get into my big black car,” she makes you zoom in on the uncomfortable racial politics of British blooze yet again (she dated Clapton, supposedly, and refused his offer to produce her), and anticipates the gender-bending black womanism of Grace Jones's “Pull Up to the Bumper.” She also augments the lyric of Cream’s “Politician” — “I want to show you what my politics are” — with her own, replacing “I support the left” with “I support the women” and changing “I’m a political man” to “I’m a political gal,” titling the new composition “Politician Man.”

Betty was lacerated for practicing the same type of sexually progressive stagecraft that made Mick Jagger a millionaire. In the '70s, white male musicians like the Stones and Bob Dylan employed black female vocalists like Merry Clayton and Regina Havas as backing singers to channel the black gospel and roots singers they admired and emulated. But Davis was larger than life, a black female rock singer who drew the spotlight, who rightfully repossessed rock and roll but rejected its vaunted space in the cultural hierarchy by fusing it with hard funk, jazz, and mystical, feminine libido. There was no demarcated path. She forged her own, which others have continued to discover for decades after. There are two takes of “I'm Ready, Willing & Able” that further demonstrate Betty's skill at laid-back hard funk, and a ballad that shows her potential as a straightforward soul singer. Like many women recording and creating in that time and place, other people’s modest understanding of women's creativity, desire and drive is what truly hemmed in the careers of these massive talents. In typical fashion, Davis offers nothing but a kiss-off for anyone who isn't feeling her freakiness: “Really / It's a pity / You can't get into me,” she chides on “Dedicated to the Press” from 1975's Nasty Gal.

Part of the promise that psychedelia held at the tail end of the 1960s was that it would open doors of understanding — between races, sexes, sexualities, and spirits. What you hear in The Columbia Years is also what you hear in Bitches Brew — a luxurious spreading-out of grooves, an irresistible expansiveness. It's hard to imagine now that jazz fusion was ever considered controversial, but at the time of Bitches Brew's release, a lot of moldy figs hated it. There were jazz fans who rejected altogether the idea of Miles Davis incorporating rock into his music in any form. They were to later eat their words and declare it a masterpiece; ahead of its time. Betty Davis went on to make three albums, the latter two self-produced, and retired from music in 1979, burned out from being known or thought of as the ex–Mrs. Miles Davis, despite having spent the last decade creating her own dynamic and blisteringly funky discography.

Betty eventually wrote her own Southern rock anthem, — “They Say I’m Different,” from her 1974 album of the same name, which she wrote and produced — a country-funk stomper about feeding slop to hogs and “humpin' to John Lee Hooker,” the perfect swamp-rock song John Fogerty has been trying to write his whole career. She makes reference to Big Mama Thornton, the artist who recorded Leiber and Stoller’s “Hound Dog” three years before it became a hit for Elvis Presley — another liberated black woman with endless talent who saw white men reap the profits of a sound she pioneered. Betty’s surrealist sense of humor, freaky tales, and acid queen persona paved the way for all kinds of artists who have embraced being “different” from the mainstream. The Columbia Years reinforces Betty Davis’s genius and her primacy as her own artist. She should have had more than a cult legacy. As it is, we can honor the work of Betty Davis that we are lucky enough to have and continue to marvel at how ahead of her time she remains.