Jazz-rock may refer to the loudest, wildest, most electrified fusion bands from the jazz camp, but most often it describes performers coming from the rock side of the equation. Jazz-rock first emerged during the late '60s as an attempt to fuse the visceral power of rock with the musical complexity and improvisational fireworks of jazz. Since rock often emphasized directness and simplicity over virtuosity, jazz-rock generally grew out of the most artistically ambitious rock subgenres of the late '60s and early '70s: psychedelia, progressive rock, and the singer/songwriter movement. The latter drew from the mellower, more cerebral side of jazz, often employing vocal as well as instrumental improvisation; this school's major figures included Joni Mitchell, Van Morrison, and Tim Buckley. Most jazz-rock, however, was played by higher-energy rock ensembles. Some of them were more jam-oriented, borrowing jazz harmonies and instruments for their extended, rock-flavored improvisations (Traffic, Santana). Others recorded jazz-flavored R&B or pop songs that used the melodic, harmonic, and rhythmic sensibilities of jazz, but weren't as interested in improvisation or instrumental virtuosity (Blood, Sweat & Tears, Chicago, Steely Dan). Still others used jazz's complexity to expand rock's musical horizons, not just in terms of instrumental technique but in crafting quirky, challenging, unpredictable compositions (Frank Zappa, the Soft Machine). The major exception was Miles Davis, the first jazz musician since the early R&B era to covet the earthy power of rock & roll and the impact it had on young audiences. Starting with 1970's Bitches Brew, Davis' early-'70s fusion workouts -- greatly inspired by Jimi Hendrix and Sly & the Family Stone -- quickly became some of the funkiest, edgiest, most aggressive jazz-rock ever recorded. While figures like Zappa and $Steely Dan continued to record jazz-rock through the '70s, the movement had essentially dissipated by the '80s, as a mellower form of fusion captured its audience.