Acid Rock
A form of psychedelic rock generally defined by harder, heavier, rawer, and distorted guitar work; lyrics with drug references; and long improvised blues jams. Its distinctions from other genres can be tenuous, as much of the style overlaps with 1960s punk, proto-metal, and early blues-based hard rock. Elements of acid rock later split into two directions, with hard rock and heavy metal on one side and progressive rock on the other. 1965–1970s.