Deep Purple sure were lucky “some stupid with a flare gun” accidentally burned down Montreux Casino in 1971 (the property owners less so), but even without classic rock radio’s number one fire-related staple, their sixth album would be one for the history books for the opening and closing tracks alone. “Highway Star” captures the joy of blasting down the highway at high speeds in a sports car and “Space Truckin’” does the same except in a van with spaceships painted on the side. In between there’s some psychedelic noodling and some bluesy noodling, and “Pictures of Home”’s pastoral pleasures shouldn’t be missed. Plus, of course, one particular four-note riff.