Acid rock is a loosely defined type of rock music that evolved out of the mid-1960s garage punk movement and helped launch the psychedelic subculture. Acid rock features a harder, louder, heavier, or rawer sound compared to other forms of psychedelic rock. Acid rock developed mainly from the American West Coast, where groups did not focus on the novelty recording effects or whimsy of British psychedelia; instead, the subgenre emphasized the heavier qualities associated with both the positive and negative extremes of the psychedelic experience.

Here are some characteristics of acid rock:

• Acid rock is a heavy type of rock music with psychedelic influences.
• Acid rock features a harder, louder, heavier, or rawer sound compared to other forms of psychedelic rock.
• Acid rock uses a lot of dissonant tones and obscure melodies and modes.
• Acid rock creates sonic textures that culminate in a psychedelic effect, sometimes.

Acid rock is generally considered a subgenre of psychedelic rock. The term "acid rock" was initially loosely defined and was used to describe the background music for acid trips in underground parties in the 1960s and as a catchall term for the more eclectic Haight-Ashbury bands in San Francisco.