Ritchie Blackmore has recalled how Mountain's 1970 debut single "Mississippi Queen" left him and Deep Purple drummer Ian Paice stunned when they first heard it in Germany, describing the moment as "we both went white." The anecdote highlights how the raw, heavy sound of American bands such as Mountain and The Allman Brothers pushed Deep Purple towards a heavier direction after their earlier psychedelic-tinged albums had underperformed, a shift that would prove pivotal to the band's success.

That heavier approach, adopted for 1970's "Deep Purple In Rock" with the band's "Mark II" line-up, reached number four in the UK charts, with follow-ups "Fireball" and "Machine Head" both hitting number one. Leslie West's guitar work on "Mississippi Queen," including its distinctive cowbell intro and "pig squeal" solos, made a lasting impression on Blackmore, and the two bands later toured together, with West known for spontaneously joining Deep Purple's sets uninvited. Decades later, their paths crossed again when Joe Lynn Turner, Blackmore's former Rainbow and Deep Purple vocalist, began collaborating with West himself.