Psychedelic rock is a style of rock music sometimes inspired by or attempting to replicate the mind-altering experiences brought on by drugs such as cannabis, psilocybin, mescaline, and especially LSD. There are also other forms of psychedelic music that started from the same roots and diverged from the prevalent rock style into electronic music.
In the history of rock music, psychedelic rock is a bridge from early blues-based rock to latter progressive rock and heavy metal, but it also drew heavily from non-Western sources such as Indian music.
13th Floor Elevators' frontman Roky Erickson was once asked by a friend to define psychedelic music. Invoking the image on the American one dollar bill, he famously replied, "It's where the pyramid meets the eye, man."citation needed]
While the first musicians to be influenced by psychedelic drugs were in the jazz and folk scenes, the first use of the term "psychedelic" in popular music was by the "acid-folk" group The Holy Modal Rounders in 1964. The first use of the word "psychedelic" in a rock music context is usually credited to The Deep, and the earliest known appearance of this usage of the word in print is in the title of their 1966 album The Psychedelic Moods of the Deep. Acid rock is often used interchangeably with psychedelic rock, but usually refers to styles bordering or overlapping with hard rock or heavy metal. Generally, psychedelic rock is more mellow.
The psychedelic sound itself had been around at least a year earlier in the live music of the Grateful Dead and Pink Floyd, Donovan's hit Sunshine Superman and the landmark single "Rain" by The Beatles.