A style of rock music inspired by or attempting to replicate the mind-altering experiences brought on by hallucinogenic drugs, 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.
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 in a rock music context is usually credited to the 13th Floor Elevators, and the earliest known appearance of this usage of the word in print is in the title of their 1966 album The Psychedelic Sounds of the 13th Floor Elevators.
Acid rock is often used interchangeably with psychedelic rock, but usually refers to stylers 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 several of the later singles and albums of the Beatles.
Key features of the style of psychedelic rock that came to public attention in 1966-67 are modal melodies, esoteric lyrics often describing dreams, visions, or hallucinations, longer songs and lengthy instrumental solos.
A major characteristic of psychedelic music is its elaborate production, often using multitrack recording with heavy reliance on electronic effects such as distortion, reverb, and reversed, delayed and/or phased sounds. Another common feature is its beat variance from traditional dance music, either through an unusual encompassing beat (as heard in Tomorrow Never Knows) or by disrupting traditional 4/4 timing with interludes (as in See Emily Play). The advent of psychedelic rock marked the emergence of the 'studio as instrument' trend, which led to extremely extended timescales for album production.
Psychedelia also had a massive impact on album art. Prior to 1967, most album covers were simple single-sleeve affairs, but album cover design was revolutionised in June 1967 with the release of Sgt Pepper's Lonely Hearts Club Band.
Psychedelic rock was heavily affected by the contemporary interest in the music of India, particularly the raga form and the classical instrumental styles of Hindustani music, which was popularised in the west by the Beatles and Ravi Shankar. With its extended, modal structures, long passages of improvisation, unusual time signatures and exotic instruments like the sitar, the tanbura and the tabla, Indian music exerted a considerable influence on western pop-rock musicians. This can be clearly heard in songs like Paint It, Black by the Rolling Stones, Hole In My Shoe by Traffic and Norwegian Wood by the Beatles.
Psychedelia began in the United States' folk scene, with New York City's Holy Modal Rounders in 1964. A similar band called Mother McCree's Uptown Jug Champions from San Francisco were influenced by the Byrds and the Beatles to switch from acoustic music to electric music in 1965. Renaming themselves the Warlocks, they fell in with Ken Kesey's LSD-fuelled Merry Pranksters in November 1965 and changed their name to the Grateful Dead the following month.
The Dead played to light shows at the Pranksters' Acid Tests, with pulsing images being projected over the group in what became a widespread practice. Their sound soon became identified as acid rock which they played at the Trips Festival at the Fillmore Auditorium in January 1966 along with Big Brother and the Holding Company.
Throughout 1966, the San Francisco music scene flourished, as the Fillmore, the Avalon Ballroom and the Matrix club began booking local rock bands on a nightly basis. The emerging San Francisco Sound made local stars of numerous bands, including the Charlatans, Quicksilver Messenger Service, Country Joe and the Fish, the Great Society and Jefferson Airplane.
Jefferson Airplane gained greater fame the following year with two of the earliest psychedelic hit singles: White Rabbit and Somebody to Love. In fact, both these songs had originated with the band the Great Society, whose singer Grace Slick left them to accept an offer to join Jefferson Airplane, taking the two compositions with her.
Although San Francisco receives much of the credit for jumpstarting the psychedelic music scene, many other American cities contributed significantly to the new genre. Los Angeles boasted dozens of important psychedelic bands, including the Byrds (notably Eight Miles High), Iron Butterfly, Love, Spirit, the United States of America, Jimi Hendrix and the Doors. New York City produced its share of psychedelic bands such as the Blues Magoos and the Blues Project. Texas (particularly Austin) is often cited for its contributions to psychedelic music, being home to the 13th Floor Elevators and others.
The Beach Boys initially seemed unlikely as psychedelic types, but their music grew more psychedelic and experimental, perhaps due in part to writer/producer/arranger Brian Wilson's increased drug usage and burgeoning mental illness. In 1966, responding to the Beatles' innovations, they produced their album Pet Sounds and later that year had a massive hit with the psychedelic single Good Vibrations.
The psychedelic influence was also felt in black music, where record labels such as Motown dabbled for a while with psychedelic soul, producing such hits as Ball of Confusion (That's What the World Is Today) by the Temptations and Reflections by Diana Ross and the Supremes.
In the UK, Donovan, going electric like Dylan, had a 1966 hit with Sunshine Superman, one of the very first overtly psychedelic pop records. Pink Floyd had been developing psychedelic rock with light shows since 1965 in the underground culture scene and in 1966 the Soft Machine formed. From a blues rock background, Cream showed their psychedelic sounds on the Disraeli Gears album, while the Jimi Hendrix Experience pushed even further into psychedelia.
By late 1965, the Beatles had also jumped onto the psychedelic bandwagong with the release of Rubber Soul, and this was strengthened further with Revolver and Sergeant Pepper. The Rolling Stones had drug references and psychedelic hints in their 1966 singles 19th Nervous Breakdown and Paint It, Black, then the fully psychedelic Their Satanic Majesties Request. Other rock bands including psychedelic elements included the Small Faces and the Who.
In the folk scene, drugs, jazz and eastern influences had featured since 1964 in the work of Davey Graham and Bert Jansch, and in 1967 the Incredible String Band's The 5000 Spirits or the Layers of the Onion developed this into full blown psychedelia.
Many of the bands that pioneered psychedelic rock left it by the end of the 1960s. The increasingly hostile political environment and the embrace of amphetamines, heroin and cocaine by the underground led to a turn toward harsher music. At the same time, Dylan released John Wesley Harding and the Band released Music from Big Pink, both albums that rejected psychedelia for a more roots-oriented approach. Many bands in England and America followed suit. Eric Clapton cites Music from Big Pink as a primary reason for quitting Cream, for example. The Grateful Dead also went back to basics and had major successes with Workingman's Dead and American Beauty in 1970.
The musicians and bands that continued to embrace psychedelia often went on to create progressive rock in the 1970s, which maintained the love of unusual sounds and extended solos but added jazz and classical influences to the mix. For example, progressive rock group Yes sprang out of three British psychedelic bands.
Also, psychedelic rock strongly influenced early heavy metal bands, Black Sabbath probably being the best example. Psychedelic rock, with its distorted guitar sound and adventurous compositions can be seen as an important bridge between heavy metal and earlier blues oriented rock.
Alongside the progressive stream, space rock bands such as Hawkwind, Arthur Brown's Kingdom Come and Gong maintained a more explicitly psychedelic course into the 1970s.
More recently, there have been a number of acts with psychedelic rock characteristics and could be termed neo-psychedelic, such as Julian Cope, Kula Shaker and Aphex Twin, but these tend to be classified under other subgenres such as experimental rock, ambient, electronic rock or alternative rock.