Acid rock

Acid rock is a loosely defined type of rock music[1] that evolved out of the mid-1960s garage punk[3] movement and helped launch the psychedelic subculture. Named after lysergic acid diethylamide (LSD), the style is generally defined by heavy, distorted guitars, lyrics with drug references, and long improvised jams. Much of the style overlaps with 1960s garage punk, proto-metal, and early heavy, blues-based hard rock.

The term is sometimes used interchangeably with "psychedelic rock", but it also specifically refers to a more musically intense subgenre or sibling of the psychedelic rock style. Compared to other psychedelic rock, acid rock features a harder, louder, heavier, or rawer sound. It developed mainly from the American West Coast, where groups did not focus on the novelty recording effects or whimsy of British psychedelia, and instead emphasized the heavier qualities associated with both the positive and negative extremes of the psychedelic experience.

As the movement progressed into the late 1960s and 1970s, elements of acid rock split into two directions, with hard rock and heavy metal on one side and progressive rock on the other. In the 1990s, the stoner metal genre combined acid rock with other hard rock styles such as grunge, updating the heavy riffs and long jams found in acid rock and psychedelic-influenced metal.