A proposed supergroup from the start, Deep Purple was assembled around the talents of classically trained organ player Jon Lord (late of the Artwoods) and guitarist Ritchie Blackmore, a stage and session ace whose resume already included names like Screaming Lord Sutch, the Outlaws and eccentric producer Joe Meek. After dispensing with original percussionist Chris Curtis and the formative band name of Roundabout, the twosome recruited bassist Nick Simper (of the Flower Pot Men) and singer Rod Evans (of the Maze), who brought with him teenage drummer Ian Paice. Deep Purple Mk. I recorded three albums, experienced an immediate U.S. breakthrough with their cover of Joe South’s “Hush,” but then seemed in danger of becoming a one-hit wonder due to mounting business, personal and creative issues — all of which brought them to a premature career crossroads.

By the summer of 1969, Blackmore, Lord and Paice were in agreement that changes in both sound and personnel were needed for there to be any hope of relaunching Deep Purple’s career. They replaced Evans and Simper with Episode Six singer Ian Gillan and bassist Roger Glover, whom they felt were better equipped to pursue a heavier new direction. Sure enough, following a brief detour into symphonic rock for Lord’s ambitious ‘Concerto for Group and Orchestra,’ the rookie duo proved to be perfect catalysts. ‘In Rock,’ ‘Fireball’ and ‘Machine Head’ are still lauded as cornerstones of hard rock and heavy metal. Still, Deep Purple’s so-called Mk. II lineup would soon buckle under the pressure of creative differences and non-stop work. After cementing their legend with 1972’s ‘Made in Japan,’ and cutting 1973’s clearly less inspired ‘Who Do We Think We Are?,’ Gillan and Glover exited, leaving Blackmore, Lord and Paice to consider their next move.

Another pair of complementary musicians arrived in former Trapeze bassist and vocalist Glenn Hughes and a relative unknown lead singer by the name of David Coverdale. Mk. III immediately recovered their top form behind 1974’s ‘Burn’ album, and performed before perhaps their biggest audience ever as headliners of the famed California Jam. Unfortunately, the familiar interpersonal bickering, fueled by escalating drug use, would again surface by year’s end, as evidenced by Purple’s less-inspired ‘Stormbringer’ follow up LP. This time, the issue was Blackmore, who did not care for the new musical influences (primarily funk-rock) permeating Deep Purple. Blackmore decided to start fresh with Rainbow, and the remaining members faced their stiffest challenge yet.