Dark drama is at the heart of Deep Purple’s pioneering heavy rock. The grandiose guitar-and-organ riffs of “Smoke on the Water” and “Black Night” are steeped in heavy funk and then booted into life by aggro drumming. There are scorching, pummeling songs (“Fireball,” “Burn”), loping, groovy songs (“Strange Kind of Woman,” “Space Truckin’”), and ponderous faux-medieval epics (“Child in Time”), but in every case the battle is between the primal power of the music and the sophisticated capabilities of its players.