Acid rock is a genre of rock music that emerged in the late 1960s in the United States. It is characterized by psychedelic and experimental sounds, along with lyrics that often explore themes of drug use and counterculture. Some synonyms for acid rock include psychedelic rock, garage rock, heavy rock, and hard rock. These terms are often used interchangeably to describe the same type of music. While acid rock may have peaked in popularity in the late 1960s and early 1970s, its influence can still be heard in contemporary rock music and has continued to inspire new generations of musicians.