Creative differences, substance abuse, different career objectives, even dating the same person - these are all factors that could make relationships between bandmates go sour, and it could take years for their differences to be resolved, if at all. There are many reasons why two people in the same band could go from being on relatively pleasant terms to hating each other. But they also happened to have a hard time seeing eye-to-eye for most of their time as bandmates and continued to throw verbal jabs at each other even after Blackmore left Deep Purple for good in 1993. Together with the rest of the "Mark II" lineup (bassist Roger Glover, keyboardist Jon Lord, and drummer Ian Paice), Gillan and Blackmore teamed up on future classics such as "Black Night," "Highway Star," and of course, that little song about smoke on the water and fire in the sky. Band members don't necessarily need to be friends in order to create classic hits in the studio and perform them onstage. For much of their existence, that applied to Deep Purple, a band that was most successful with two strong personalities in the same lineup - frontman Ian Gillan and guitarist Ritchie Blackmore.