Deep Purple Survived a Seemingly Endless Series of Lineup Changes and a Dramatic Mid-career Shift from Grandiose Progressive Rock to Ear-shattering Heavy Metal to Emerge as a True Institution of the British Hard Rock Community; Once Credited in the Guinness Book of World Records as the Globe"s Loudest Band, their Revolving-door Roster Launched the Careers of Performers Including Ritchie Blackmore, David Coverdale, and Ian Gillan.