Acid Rock is a subgenre of rock music that developed in the mid-1960s, influenced by psychedelic culture. It is characterized by lengthy compositions, extensive improvisations, using intense feedback and distortion on guitars. It often includes abstract or transcendental lyrics, while sonically it may involve extensive use of effects and innovative production. Popular artists of the genre include bands like Jefferson Airplane and Grateful Dead, who were associated with the '60s culture and the counterculture of the era.