Davis' influences included late-1960s acid rock and funk artists such as Sly and the Family Stone, James Brown, and Jimi Hendrix, many of whom he met through Betty Mabry (later Betty Davis), a young model and songwriter Davis married in September 1968 and divorced a year later. The musical transition required that Davis and his band adapt to electric instruments in both live performances and the studio. By the time In a Silent Way had been recorded in February 1969, Davis had augmented his quintet with additional players. At various times Hancock or Joe Zawinul was brought in to join Corea on electric keyboards, and guitarist John McLaughlin made the first of his many appearances with Davis. By this point, Shorter was also doubling on soprano saxophone. After recording this album, Williams left to form his group Lifetime and was replaced by Jack DeJohnette. Six months later an even larger group of musicians, including Jack DeJohnette, Airto Moreira, and Bennie Maupin, recorded the double LP Bitches Brew, which became a huge seller, reaching gold status by 1976. This album and In a Silent Way were among the first fusions of jazz and rock that were commercially successful, building on the groundwork laid by Charles Lloyd, Larry Coryell, and others who pioneered a genre that would become known as jazz-rock fusion. During this period, Davis toured with Shorter, Corea, Holland, and DeJohnette. The group's repertoire included material from Bitches Brew, In a Silent Way, and the 1960s quintet albums, along with an occasional standard.  In 1972, Davis was introduced to the music of Karlheinz Stockhausen by Paul Buckmaster, leading to a period of new creative exploration. Biographer J. K. Chambers wrote that "the effect of Davis' study of Stockhausen could not be repressed for long. . . . Davis' own 'space music' shows Stockhausen's influence compositionally." His recordings and performances during this period were described as "space music" by fans, by music critic Leonard Feather, and by Buckmaster, who described it as "a lot of mood changes—heavy, dark, intense—definitely space music." Both Bitches Brew and In a Silent Way feature "extended" (more than 20 minutes each) compositions that were never actually "played straight through" by the musicians in the studio. Instead, Davis and producer Teo Macero selected musical motifs of various lengths from recorded extended improvisations and edited them together into a musical whole that exists only in the recorded version. Bitches Brew made use of such electronic effects as multi-tracking, tape loops, and other editing techniques. Both records, especially Bitches Brew, proved to be big sellers. Starting with Bitches Brew, Davis' albums began to often feature cover art much more in line with psychedelic art or black power movements than that of his earlier albums. He took significant cuts in his usual performing fees in order to open for rock groups like the Steve Miller Band, the Grateful Dead, and Santana. Several live albums were recorded during the early 1970s at these performances: Live at the Fillmore East, March 7, 1970: It's About That Time (March 1970), Black Beauty (April 1970), and Miles Davis at Fillmore: Live at the Fillmore East (June 1970). By the time of Live-Evil in December 1970, Davis' ensemble had transformed into a much more funk-oriented group. Davis began experimenting with wah-wah effects on his horn. The ensemble with Gary Bartz, Keith Jarrett, and Michael Henderson, often referred to as the "Cellar Door band" (the live portions of Live-Evil were recorded at a Washington, DC, club by that name), never recorded in the studio, but is documented in the six-CD box set The Cellar Door Sessions, which was recorded over four nights in December 1970.  In 1970, Davis contributed extensively to the soundtrack of a documentary about the African-American boxer heavyweight champion Jack Johnson. Himself a devotee of boxing, Davis drew parallels between Johnson, whose career had been defined by the fruitless search for a Great White Hope to dethrone him, and Davis' own career, in which he felt the musical establishment of the time had prevented him from receiving the acclaim and rewards that were due him. The resulting album, 1971's A Tribute to Jack Johnson, contained two long pieces that featured musicians (some of whom were not credited on the record) including guitarists John McLaughlin and Sonny Sharrock, Herbie Hancock on a Farfisa organ, and drummer Billy Cobham. McLaughlin and Cobham went on to become founding members of the Mahavishnu Orchestra in 1971. As Davis stated in his autobiography, he wanted to make music for the young African-American audience. On the Corner (1972) blended funk elements with the traditional jazz styles he had played his entire career. The album was highlighted by the appearance of saxophonist Carlos Garnett. Critics were not kind to the album; in his autobiography, Davis stated that critics could not figure out how to categorize it, and he complained that the album was not promoted by the "traditional" jazz radio stations.  After recording On the Corner, Davis put together a new group, with only Michael Henderson, Carlos Garnett, and percussionist Mtume returning from the previous band. It included guitarist Reggie Lucas, tabla player Badal Roy, sitarist Khalil Balakrishna, and drummer Al Foster. It was unusual in that none of the sidemen were major jazz instrumentalists; as a result, the music emphasized rhythmic density and shifting textures instead of individual solos. This group, which recorded in the Philharmonic Hall for the album In Concert (1972), was unsatisfactory to Davis. Through the first half of 1973, he dropped the tabla and sitar, took over keyboard duties, and added guitarist Pete Cosey. The Davis/Cosey/Lucas/Henderson/Mtume/Foster ensemble would remain virtually intact over the next two years. Initially, Dave Liebman played saxophones and flute with the band; in 1974, he was replaced by Sonny Fortune. Big Fun (1974) was a double album containing four long improvisations, recorded between 1969 and 1972. Similarly, Get Up With It (1974) collected recordings from the previous five years. Get Up With It included "He Loved Him Madly", a tribute to Duke Ellington, as well as one of Davis' most lauded pieces from this era, "Calypso Frelimo". It was his last studio album of the 1970s. In 1974 and 1975, Columbia recorded three double-LP live Davis albums: Dark Magus, Agharta, and Pangaea. Dark Magus captures a 1974 New York concert; the latter two are recordings of consecutive concerts from the same February 1975 day in Osaka. At the time, only Agharta was available in the US; Pangaea and Dark Magus were initially released only by CBS/Sony Japan. All three feature at least two electric guitarists (Reggie Lucas and Pete Cosey, deploying an array of Hendrix-inspired electronic distortion devices; Dominique Gaumont is a third guitarist on Dark Magus), electric bass, drums, reeds, and Davis on electric trumpet and organ. These albums were the last he was to record for five years. Davis was troubled by osteoarthritis (which led to a hip replacement operation in 1976, the first of several), sickle-cell anemia, depression, bursitis, ulcers, and a renewed dependence on alcohol and drugs (primarily cocaine), and his performances were routinely panned by critics throughout late 1974 and early 1975. By the time the group reached Japan in February 1975, Davis was nearing a physical breakdown and required copious amounts of alcohol and narcotics to make it through his engagements. Nonetheless, as noted by Richard Cook and Brian Morton, during these concerts his trumpet playing "is of the highest and most adventurous order." After a Newport Jazz Festival performance at Avery Fisher Hall in New York on July 1, 1975, Davis withdrew almost completely from the public eye for six years. As Gil Evans said, "His organism is tired. And after all the music he's contributed for 35 years, he needs a rest."  Davis characterized this period in his memoirs as a colourful time when wealthy women lavished him with sex and drugs. In reality, he had become completely dependent on various drugs, spending nearly all of his time propped up on a couch in his apartment watching television, leaving only to find more drugs. In 1976, Rolling Stone reported rumours of his imminent demise. Although he stopped practicing trumpet on a regular basis, Davis continued to compose intermittently and made three attempts at recording during his exile from performing; these sessions (one with the assistance of Paul Buckmaster and Gil Evans, who left after not receiving promised compensation) bore little fruit and remain unreleased. In 1979, he placed in the yearly top-ten trumpeter poll of Down Beat. Columbia continued to issue compilation albums and records of unreleased vault material to fulfil contractual obligations. During his period of inactivity, Davis saw the fusion music that he had spearheaded over the past decade enter into the mainstream. When he emerged from retirement, Davis' musical descendants would be in the realm of New Wave rock, and in particular the styling of Prince.