The song marked a radical departure for the Beatles, as the band fully embraced the potential of the recording studio without consideration for reproducing the results in concert.

[11] It features an Indian-inspired modal backing of tambura and sitar drone and bass guitar, with minimal harmonic deviation from a single chord, underpinned by a constant but non-standard drum pattern; added to this, tape loops prepared by the band were overdubbed "live" onto the rhythm track.

"Tomorrow Never Knows" was an early and highly influential recording in the psychedelic and electronic music genres, particularly for its pioneering use of sampling, tape manipulation and other production techniques.

[17] In a television interview in early 1964, Starr had uttered the phrase "Tomorrow never knows" when laughing off an incident that took place at the British Embassy in Washington, DC, during which one of the guests had cut off a portion of his hair.

[14][nb 1] The harmonic structure is derived from Indian music, a genre that Harrison had introduced to the Beatles' sound late in 1965 with his sitar part on "Norwegian Wood", and is based on a high volume C drone played on a tambura.

[34][nb 2] Despite this limitation, musicologist Dominic Pedler sees the Beatles' harmonic ingenuity displayed in the upper harmonies – "Turn off your mind", for example, is a run of unvarying E melody notes, before "relax" involves an E–G melody-note shift and "float downstream" an E–C–G descent.

[15] Geoff Emerick, who was promoted to the role of the Beatles' recording engineer for Revolver, recalled that the band "encouraged us to break the rules" and ensure that each instrument "should sound unlike itself".

[47] In the description of musicologist Russell Reising, the "meditative state" of a psychedelic experience is conveyed through the musical drone, enhancing the lyrical imagery, while the "buzz" of a drug-induced "high" is sonically reproduced in Harrison's tambura rhythm and Starr's heavily treated drum sound.

[81][82][nb 5] Tony Hall, a music industry figure and journalist with a reputation for predicting trends, was also given a preview of the song, along with other tracks from early in the sessions.

[84] Writing in his column for Record Mirror in the issue dated 14 May, Hall especially highlighted "The Void" when describing the new songs as "the most revolutionary ever made by a pop group".

"[85] "Tomorrow Never Knows" was the most experimental and psychedelic track on Revolver, in both its structure and production ... [T]he lyrics were philosophical, existential, sometimes inscrutable reflections on the state of being: a heavy subject for popular music, whether in 1966 or any other year.

[88][89] According to author Mark Hertsgaard, as the first song recorded during the Revolver sessions, its sequencing ensures that the track serves as "the summit to which the entire album ascends".

[90] In his design for the LP cover, Klaus Voormann drew inspiration from the song, recognising the need for artwork that would capture the Beatles' new direction[91] and the avant-garde aspect of the recording.

"[93] In an interview in October 1966, Harrison described the song as "easily the most amazing new thing we've ever come up with", but acknowledged that it might represent "a terrible mess of a sound" to listeners who approached the track without "open ears".

[96][97] The editor of the Australian teen magazine Mirabelle wrote: "Everyone, from Brisbane to Bootle, hates that daft song Lennon sang at the end of Revolver.

"[77] Recalling the release in his 1977 book The Beatles Forever, Nicholas Schaffner commented that whereas the group's more traditional fans warmed to McCartney's new songs, "some people thought Lennon was sprouting complete gibberish, and concluded that the poor lad had slid off the deep end.

"[104] Disc and Music Echo's review of Revolver took the form of a track-by-track rundown by Ray Davies of the Kinks, who, in author Steve Turner's opinion, took the opportunity to air his longstanding bitterness towards the Beatles.

[107] Writing in the recently launched Crawdaddy!, Paul Williams derided "Tomorrow Never Knows" and the album's single, "Yellow Submarine", saying of Lennon's song: "A good artist doesn't publish first drafts.

He said the lyrics were a "curious sort of poetry" that conveyed the concept of "pop-music as a substitute, both for jungle emotions and for the consolations of religion", as teenagers followed in the long societal tradition of disengaging the mind and surrendering "to the tribal leader, the priest, or now the pop-singer".

[118][119] Reviewing the album for PopMatters, Zeth Lundy wrote: "The 'Within You Without You'/'Tomorrow Never Knows' mash-up, perhaps the most thrilling and effective track on the entire disc, fuses two especially transcendental songs into one: ... a union of two ambiguous, open-ended declarations of spiritual pursuit.

[122] Nicholas Schaffner said that listeners who had been confused by the song's lyrics were most likely unfamiliar with hallucinogenic drugs and Timothy Leary's message, but that the transcendental quality became clear during the build-up to the 1967 Summer of Love.

[124] Ian MacDonald says that the song's message represented a revolutionary concept in mainstream society in 1966, and by introducing LSD and Leary's "psychedelic revolution" to Western youth, it is "one of the most socially influential records The Beatles ever made".

[125] He adds: "'Tomorrow Never Knows' launched the till-then élite-preserved concept of mind-expansion into pop, simultaneously drawing attention to consciousness-enhancing drugs and the ancient religious philosophies of the Orient, utterly alien to Western thought in their anti-materialism, rapt passivity, and world-sceptical focus on visionary consciousness.

[129] In the opinion of former Mojo editor Paul Trynka, the track benefited most from the Beatles' ability to channel their ideas into a recognisable song form, a discipline that ensured their psychedelic recordings were superior to those by the Grateful Dead and other contemporary San Francisco acts.

[7] Music historians David Luhrssen and Michael Larson say that with Revolver the Beatles "erased boundaries of time and culture", adding: "Ancient met modern on 'Tomorrow Never Knows' as sitars encountered tape loops.

'Tomorrow Never Knows' reintroduced the sustained repetition of the drone, absent in Western music since the Middle Ages and only recently discovered by avant-garde composer La Monte Young.

[135][nb 8] He identifies its studio effects and musical form as central to Pink Floyd's "Pow R. Toc H." and recognises the same use of extreme tape-speed manipulation in subsequent recordings by Jimi Hendrix and Frank Zappa, and backwards tapes in the work of Hendrix, Pink Floyd, the Byrds, the Who, the Electric Prunes, Spirit, Tomorrow, Soft Machine and the First Edition.

He also identifies the Leslie-treated vocal as a precedent for similar experimentation by Hendrix, the Grateful Dead, the Moody Blues, Cream, Yes, Led Zeppelin and Black Sabbath.

[152] Sung by comedians Peter Cook and Dudley Moore, both of whom are dressed in Indian clothing, the song evokes the seagull sounds of "Tomorrow Never Knows" through the presence of a bird squawking in the studio, and includes lyrics playing on the sensory contradictions of lines such as "Listen to the colour of your dreams" from the Beatles track.

Whether it is true or not, The Wall Street Journal reported that Lionsgate claimed the 2012 use of this song marked "the first time a master recording by the Beatles has been licensed for a television show.