Tell Me That You’ve Heard Every Sound There Is –
The Harmonic Series in the Music of the Beatles
The Beatles as both a musical and cultural phenomena of the late 20th century has been well documented, and their music of late has been examined thoroughly in music journals and academia. However, despite the detailed analysis of their music, a more fundamental principle comes to mind in regard to their overriding sonic qualities: could the appeal of the quartet’s music be attributed towards a harmonic richness, unconsciously based upon the overtones of the harmonic series? This research project aims to explore this claim by way of examining both the harmonic and melodic detail of a number of key songs from their repertoire, consider the Beatles evolving use of instrumentation over their career in regard to timbre and tonality, and also investigate studio techniques, especially in regard to harmonic exploration. I expect these findings will help to shed light upon the allure of the Beatles music, not only in terms of songcraft, but in regard to providing us with a recognisable ‘sonic template’ which has implications for both music production and the creation of popular music in years to come.
The initial ‘spark’ for this investigation came from an essay by Emeritus Professor of Music, Sir Peter Platt, in which he examines the music of Debussy in relation to the harmonic series, noting that in conversation with his harmony teacher Guiraud, Debussy felt his harmonic sensibilities lay somewhere ‘beyond a frontier’. Platt clearly believes that Debussy’s ‘quiet revolution’ can be explained through a ‘template’ of the harmonic series ‘governing our innate and general sense of pitch relations’. He also recognises that using harmonics as a template allowed Debussy to ‘break down the typically western V-I (Dominant-Tonic) mind-set’, and submerge it within:
a procedure based on a more general confluence of melody and harmony—a confluence that potentially anyone accustomed to listening to harmonised music could understand precisely because it is strongly related to the harmonic series to which the human ear/brain mechanism seems specially responsive.
This notion resonated with my own thoughts on the harmonic series as a ‘template’ for much of the worlds music; I was also reassured to note that Platt recognised the concept has often received ‘mixed press’, as my own investigations had initially met with a need for rigorous scientific validation via an examination of Pythagorean theory, ‘just’ intonation and various anomalies between the well-tempered system and the harmonic series. Although relevant, I feel my research is primarily musical in nature (in the same manner as Platt’s essay) and do not feel anything more than a cursory acknowledgement of the physical attributes of the phenomena is warranted in this instance, and only in regard to aspects of melody, harmony and timbre.
Although Platt highlights Debussy’s writing including Prelude a l’ Apres-midi d’un faune as relating to the harmonic series up to and including the 12th partial, I am inclined to look at the series as it relates to the Beatles more as a gradual unfolding awareness to the possibilities of harmonic extension. This appears to be most apparent around the time of the albums Rubber Soul (1965) and Revolver (1966), and perhaps unsurprisingly, around the time of George Harrisons exposure to classical Indian music and the influence of Ravi Shankar. This is seen by K.G. Johansson in his essay The Harmonic Language of the Beatles as an ‘exploding (of) functional harmony’ and Ger Tillikens in his essay A flood of flat-sevenths, who notes the use of flattened seventh chords (bVII) in the Beatles music from this period as an indication of an extended harmonic language. Although seen as early as 1963 in compositions such as ‘P.S. I Love You’ and appearing more adventurously in the opening to ‘Hard Days Night’ (1964), the chord is particularly in evidence around the time of Revolver (1966) in no less than half of the albums songs, notably in material by Harrison and Lennon. The presence of the flat seventh is usually an indicator of modal harmony, and Tillikens notes the prevalence of what he refers to as ‘Neapolitan’ chords (bIII, bVI and bVII chords), indicating that this may be a hangover from blues inflections, but also emphasizes the microtonal differences in the 7th scale degree delivery depend on the underlying chord (whether relating to the tonic, sub-dominant or dominant), highlighting the ambiguity of the 7th and its respective differences in the harmonic series and even-tempered scales.
In The Beatles as Musicians, Walter Everett notes George Harrison’s increasing use of added sixth and added ninth chords, drawing attention again to the ‘Hard Days Night’ opening chord (bVIIadd9) as an indication of an emerging harmonic awareness, but also points to the ringing tones of his Rickenbacker 12-string guitar, “four of its courses tuned in brilliant octaves”, as a instrumental extension of this – he also observes that
the vibrant Fender Stratocaster (guitar) introduced in early 1965 became a staple of the Beatles sound two years thence and can also be seen as a precursor to the exceedingly brilliant waveforms of the sitar that Harrison introduced in Rubber Soul and used as his main instrument in 1966-68.
The Beatles awareness of Indian classical music via Harrison, although in a manner that to Indian musicians would be considered simplistic, was nonetheless important to their expanding harmonic awareness. Again, according to Tillikens;
In combination with the tonic, the flat-seventh proves to be a good chord to imitate an Indian sound, at least to Western ears, as both variants of this chord offer some of the same microtonal distances that are familiar to the idiom of Indian music.
In Revolver’s closing track ‘Tomorrow Never Knows’, the single C chord accompanied by a mixolydian melody, appears to confirm an embracing of the harmonic series, by reducing the harmonic material to its most basic, but within a spectrally dense arrangement employing crashing cymbals and drums, droning tanpuras, a pulsating bass, organ, distorted backwards guitar, tape loops, sweeping scalic arpeggios and above everything, Lennon’s heavily distorted vocal. The overall effect is hypnotic, trance-like; as Ian MacDonald indicates in Revolution in The Head, the sonic and timbral considerations of this recording were as important as the song itself, with Starr’s mesmeric drumbeat “performed mainly on a pair of slack-tuned tom-toms – damped, compressed, and recorded with massive echo – it created the image of a cosmic tabla played by a Vedic deity riding in a stormcloud”. MacDonald’s assessment captures how far the group had come both in terms of songcraft and production in the three short years since the release of ‘Please Please Me’, with allusions to Indian ragas and scales, sophisticated harmonic language and experimentation with new technologies, instrumentation and timbre.
Andy Babuik’s exhaustively detailed Beatles Gear offers insights into the Beatles choice of instruments and, not unimportantly, amplification, for the sound of an electric guitar is the sum of both the instrument and the amplifier it is run through. Apart from Harrison and Lennon’s choice of Gretsch and Rickenbacker guitars, notable for their ringing tone, the British AC30 Vox amplifiers, later with added ‘top boost’, complemented the Beatles sound, adding further high-order harmonics to the already bright soundscape. Once overdriven (further gain added at the amplifiers input stage) these amplifiers distort in a warm, harmonically-saturated tone, more evident in later tracks such as ‘Paperback Writer’ (1966), adding further harmonic complexity to the Beatles sound palette. Already well versed by this stage in techniques designed to extend the guitars timbre (for example, the use of buzzing guitar feedback, droning on the 1st harmonic on the A string in the opening to ‘I Feel Fine’ in 1964), the Beatles with the aid of producer George Martin and recording engineer Ken Townsend, developed another recording technique to further enrich their sound – ADT (artificial double tracking) was employed at first on voice and later instruments, but had a remarkable sonic effect, according to Mark Lewisohn in The Complete Beatles Recording Sessions;
In photography, the placement of a negative directly over another does not alter the image. The two become one. But move one slightly and the image widens. ADT does this with tape. One voice laid perfectly on top of another produces one image. But move the second voice by just a few milliseconds and two separate images emerge.
The technique effectively describes what later became known as ‘flanging’ or phase-shifting, an auditory effect resulting in combining of two identical signals, with one modulated by a variable oscillator – at its simplest, a simple doubling of the existing signal, at its extreme, an audible sweep of the frequency range in the sum difference of the two signals, clearly evident on songs such as ‘Lucy In The Sky With Diamonds’ and ‘Blue Jay Way’. Another similar ‘phasing’ effect was derived from running a microphone through a Leslie speaker cabinet, containing ‘a rotating horn’ with which ‘the speed of the rotation could controlled by the player’ according to Babuik – though designed to be used in conjunction with a Hammond organ, the Beatles would put vocals and guitars through the cabinet to provide the sweeping, atmospheric effect. All of these recording techniques added to the spectral content of their recordings and no doubt helped to extend their harmonic language further than ever before.
K.J. Johansson’s essay The Harmonic Language of the Beatles analyses, among other aspects, the frequency of use of certain chords employed by the Beatles in their songwriting: like Tillikens, he observes the regular occurrence of not only the bVII chord, but also the non-diatonic major II chord. After I, IV, V and the diatonic minors of ii and vi, these are the most frequently used chords in the Beatles catalogue, and if we relate this to the harmonic series, the bVII chord introduces the 7th harmonic (b7 scale degree) and with the II chord, the 11th harmonic (#11 scale degree). He also notes that the bVII and II chords are convenient chord substitutes according to their close proximity within the circle of fifths (the II being the dominant of the V chord, the bVII being the subdominant of the IV chord) and that the idiomatic nature of the guitar and its tuning lends itself to the open major chords of C, G, D, A and E, and the minor chords of Am, Em and Dm, again, located in relatively close proximity in the circle of fifths. Wilfred Mellers in Twilight of The Gods: The Beatles in Retrospect, also writes that
the wide-eyed, open-eared effects created in Beatles songs by mediant relationships and side-stepping modulations are the empirical product of the movement of melody, modally conceived, and of the behaviour of the hands on guitar string or keyboard.
This aspect of the Beatles music should perhaps not be forgotten: for all its apparent sophistication, the instrumentation of Beatles (and many rock bands) is at its core a simple confluence of vibrating string instruments and drums, derived from early folk instruments, yet amplified and distorted, which only increases their harmonic content. Mellers also writes “the amplification, in more recent pop, tends to intensify the primitivism, because electronics may create a nightmarish inflation of the pitch distortions expressively endemic to folk music”, and given the Beatles choice of instrumentation, in a simplistic sense we could link the harmonic series purely to the physical nature of their instruments.
Stephen Valdez, in his essay Revolver as a Pivotal Artwork, also notes that the Beatles unique style of vocal harmonization is directly attributable to
the chords played on their accompanying instruments. Because they principally used guitars to accompany themselves, the resulting harmonies the Beatles sing are often based on the tunings of those instruments – fourths, fifths and thirds.
Certainly, given the dominance of electric guitars in their early recordings, augmented with an occasional piano or harmonica, it should perhaps come as no surprise that the underlying harmonies for many of the Beatles songs would display rich tone colours, resulting from the overlapping and mixing of diatonic guitar chords, extending into the territory of added 6ths, 9ths and suspended 4ths. But we must also remember that despite this thorough examination of instrument idiomatics, modes and harmonic and melodic interplay, an examination of the Beatles sound environment is almost of equal importance in this enquiry to any analysis of their music. From 1966 onward, the studio and the production techniques of producer George Martin and engineers such as Geoff Emerick and Ken Townshend at Abbey Road, were a crucial aspect of the creation of the Beatles recordings, and their recordings would have suffered under the auspices of lesser individuals. As self trained musicians, the Beatles instinctively wrote and arranged from a sonic palette, not a theoretical one, and were largely trusting their ears, hearts and minds in their creative practice. I would surmise there is a danger in approaching this analysis only from a theoretical point of view, because although it may go some way to explaining why a particular chord change works, it ignores the spectral and acoustic content of the recordings in which the song is placed, which in this examination of harmonic series content in the Beatles output, is our primary point of reference.
To see the harmonic series at work within the musical output of the Beatles, it may be timely at this point to remind oneself of its basic properties (Fig. 1)
The Harmonic Series (in C)
If we look at the series in purely musical terms, in line with Platt’s methodology of a harmonic ‘template’ governing many of Debussy’s compositions, we can easily see how pitch relationships within the series will lend themselves to a variety of chord colours, notably:
- Perfect fifths (2nd and 3rd, 4th and 6th, 8th and 12th partials) and fourths (3rd and 4th, 6th and 8th, 9th and 12)
- Major triad (4th, 5th, 6th partials)
- Minor triad (6th, 7th, 9th partials)
- Diminished triad (5th, 6th, 7th partials)
- Augmented triad (7th, 9th, 11th partials)
- Dominant 7th chord (4th, 5th, 6th, 7th partials)
- Dominant 9th chord (4th, 5th, 6th, 7th, 9th partials)
- Added 6th chord (8th, 10th, 12th, 13th partials)
- Added 9th chord (4th, 5th, 6th, 9th partials)
- Suspended 4th chord (6th, 8th, 9th partials)
All of these chords feature particularly to the harmonic palette of the Beatles, though some that Platt has included in his analysis of Debussy I have chosen to omit, namely the Wagnerian ‘Tristan’ chord, or minor triad with an added 6th (6th, 7th, 9th, 10th partials) and a fair portion of the whole tone scale (7th, 8th, 9th, 10th, 11th), as this more sophisticated use of tone colour rarely appears on a Beatles recording, though can’t be entirely discounted (as Walter Everett notes in his whole tone scale analysis of I Am The Walrus). One would also expect, given the progression of notes within the series up to the 7th partial, that there would be some evidence of modal harmony, in particular the mixolydian mode, given the flattened 7th scale degree, and we will see this emerge in the examples to come. It should also be noted that the sharp 11th, or tritone (11th partial), departs most radically from the even-tempered scale, up to -49 cents or nearly a quarter tone, so it also perhaps displays some interchangeability with the perfect 4th. Also note that beyond the 12th partial, in line with logarithmic nature of the series, the tones begin to cluster so tightly together as to become almost audibly indiscriminate, and for all practical purposes of this essay, I have restricted my analysis to the more obvious partials indicated in Figure 1.
Although I observe harmonic series content emerging more prominently from the albums Rubber Soul and Revolver onwards, we can see its beginnings in the Beatles very first single, ‘Love Me Do’ (1962). Despite an outwardly simple appearance, the song displays several harmonic tricks that contribute both to its appeal and gives us signposts toward what was to follow. It launches directly into a country swing feel, with acoustic guitars, bass and drums, but it is the searing harmonica motif that takes us to the first glimpse of the series, by jumping straight to F natural, the flattened 7th degree of G major and 7th partial of the series, falling via E and D and arriving on the root of G. This is the ‘hook’ that initially pulls us in, and an indicator that although the tune is largely diatonic, it plays with our expectations from the outset, introducing a dissonance that exposes the songs blues roots and lays bare the first seven partials of the harmonic series. From here, the chords stay within a standard I-IV oscillation, until our second ‘hook’ arrives on the expected V chord, the ‘plea-e-e-ease…’ vocal harmony of Lennon and McCartney, with the lower line of Lennon’s pulling away from the sustained high tonic G of McCartney’s that holds our audible interest. This neat vocal trick, no doubt learnt from the Everly Brothers in songs like ‘Cathy’s Clown’ (“minus the refinement” notes Tim Riley in Tell Me Why) and which recurs in later songs such as ‘Please Please Me’, and ‘Sgt Peppers Lonely Hearts Club Band’, introduces the idea of a constant tone with a harmony line moving against it, not unlike the drone note that sits underneath Indian classical music or Scottish bagpipe melodies, and the early signs of an inclination towards modal harmony and a gentle nod toward the harmonic series.
The idea of a constant tone running through a series of chords to provide harmonic colour (Lennon remarked that he would sometimes “grab a note and ram it home”) is a device favored both by Lennon and Harrison and appears early in ‘A Hard Days Night’ (1964). The ambiguous, opening F9/D (or G7sus4/D – this much discussed chord open to interpretation, see Dominic Pedler’s chapter in The Songwriting Secrets of the Beatles) nails its modal colours to the mast from the outset, with the following two turnarounds of the verse positioning the song in G mixolydian (we will examine mode more closely in the following section). Notice the D droning throughout however (G-Cadd9-G-F6-G) emphasized in Lennon’s melody, eventually jumping from the D to the F (b7), on ‘wor-kin’,…’ to drop to B natural in ‘dog’. This early appearance of a drone, or pedal point, would emerge later as an underlying D in the guitar introduction (D-E7-G-D) of ‘Eight Days a Week’ (1964) and as a held G over the G-Dsus4-F9-G-C-F9 verse sequence of ‘You’ve Got To Hide Your Love Away’ (1965). However, the drone reaches it’s apex on their next two albums – in the underlying E of the sitar in ‘Norwegian Wood’, the insistent A ringing through ‘If I Needed Someone’, the driving guitar and organ motif throughout the bridge of ‘The Word’ on Rubber Soul (1965), and in many of the songs on Revolver (1966), notably ‘Taxman’ (guitar solo and vocal harmonies), ‘Love You To’ (vocal harmonies and Indian instrumentation), ‘She Said She Said’ (the feedback ‘A’ appearing throughout), ‘Dr Robert’ (the organ pedal tone running throughout the bridge), ‘I Want To Tell You’ (the ostinato A through the guitar motif and ‘Indian-style’ vocal harmonies) and most overtly on the closing track, ‘Tomorrow Never Knows’, with its pedal point of tamboura and bass seemingly fixed to C for nearly three minutes. Although the only song on the album with a drone that runs for its entirety, as the first track recorded, its presence is felt throughout, and as Alan Pollack notes, “the sequencing of the entire album works toward this song”. Everett also notes a cyclic nature to proceedings, as “the circular wheels in the poetry of the track… are perfectly suggested by cyclic tape loops, backwards tapes and unending drones”, ultimately reflected in the albums title. It would surface later in Harrison’s Indian-laced songs such as ‘Within You Without You’ and ‘The Inner Light’ (1967/68), but also emerges as a harmonic linking device in everything from ‘Dear Prudence’ and ‘It’s All Too Much’ (1968) to ‘The End’ (1969), invariably within a modal context.
Mode and bVII, v and II chords
Another indication of the harmonic series is the increasing emergence of bVII chords, as noted previously by Tillikens. A non-diatonic chord in a major key, the scale degrees align with the 7th and 9th partials (and possibly the 11th partial, see above) and the mixolydian mode, often serving as substitute V or a dominant preparation. Although not an outright indicator of harmonic series content, its tonality suggests its presence, and unsurprisingly, it appears more frequently on the aforementioned middle-period albums. We have already shown the flat seven chord making its presence in ‘A Hard Days Night’, but as Pedler points out, it was “a very specific device at the heart of the revolution”, emerging as an alternate dark flavor in early songs such as ‘All My Loving’ (as the dominant preparation for “I’ll always be true…”: ii-bVII-V7) and as a dramatic undertone in ‘P.S. I Love You’ (‘You, you you’: bVI-bVII-I). However, by Revolver the bVII had become virtually synonymous with Beatles sound, appearing on no less than eight of the albums songs (those noted previously) with addition of two McCartney songs, ‘For No One’ and ‘Got To Get You Into My Life’. McCartney’s use of a bVII is different in that he uses the chord more as additional colour in transition, preferring to move onward in line with his melodic tendencies, whereas Lennon will happily stay in one mode for the duration, as in ‘She Said She Said’, where the cycle of I-bVII-IV throughout the verse/refrain is only interrupted by a shift, harmonically and metrically, to the dominant minor (v) in the bridge (‘when I was a boy…’), again emphasising the flat 7 scale degree. Despite the economy of chords, the spectrally dense arrangement, with its crashing cymbals, heavily compressed drums and ringing guitars, reinforces the series on several levels at once. The dominant minor would feature again soon in a more sophisticated context as the opening phrase in ‘Strawberry Fields Forever’ (‘Let me take you down, cause I’m going to…’: I-v).
Johansson also notes the frequency of the II chord in the Beatles oeuvre, placed just after the bVII in popularity, and this non-diatonic (but harmonic series related) chord with its b5 (or #11) becomes noticeable on tracks such as the aforementioned ‘Eight Days A Week’ and ‘I’ll Follow The Sun’ sometimes as a dominant preparation, but more often moving to the IV chord. This Beatles ‘trademark’ appears on Rubber Soul in ‘You Won’t See Me’ and on Revolver in ‘Dr. Robert’ and ‘I Want To Tell You’. Although not as blatant an indicator as the bVII chord, the II chord nonetheless draws our ear to an alternate tone colour lying within the upper realms of the series, lending a ‘bright’ colour to an otherwise diatonic sequence.
Guitar sounds and studio technology
To place Rubber Soul and Revolver in historical context, there were exotic flavors apparent in other releases in the UK around this time. The Kinks ‘See My Friends’ and the Yardbirds ‘Heart Full Of Soul’ (both 1965) featured quasi-Indian flavored guitar riffs, and following George Harrison’s use of the sitar in ‘Norwegian Wood’, there was a rapid uptake of what would soon be termed ‘raga-rock’, notably by the Rolling Stones and the Byrds. What should also be recognised however, is that the evolving timbre of electric guitar sounds leading up to this point. Advances in the development of guitar amplification, guitar technique (use of feedback, distortion), types of guitar (12-string electric) effects (such as ‘fuzz’ boxes and echo units) and studio technology (the use of compression, limiting, ADT) all affected the guitars timbre. Compression enables the sustaining of notes on an electric guitar, as does amplifier distortion (lending to drone qualities), and effects such as ADT and phase shifting widen the spectral image, particularly in stereo, and introduce high order harmonics. Following the Beatles use of guitar feedback on ‘I Feel Fine’ (1964), the tonal quality of guitars begins to feature more prominently in their recordings, and by the time of Revolver, guitar timbre is more carefully considered in the overall soundscape, partly thanks to the studio techniques of the newly appointed Geoff Emerick as chief sound engineer at Abbey Road studios. Apart from ADT, manipulation of the magnetic tape onto which recordings were made was becoming more commonplace: the single ‘Rain’ (1966) recorded during the Revolver sessions, features a backwards vocal (lifted from the first verse, adding to the cyclic quality of proceedings) and also displays manipulation of tape speed. Apart from the obvious slowing or speeding up of tempo, this also has the effect of changing the timbre of instruments; as noted by Everett on the former:
Lennon’s distorted Gretsch Nashville guitar… recorded much faster than heard, introducing a subtle but rich tone of queasy hesitation that could be likened to the nausea of an acid trip, in the center (of the stereo image): the composers lead vocal, recorded about a major second lower than heard, resulting in the brilliant iridescence of an acid-streaked sunshine, is heard on the left.
The Beatles introduction of additional instrumentation added to their sonic palette: beginning with the use of string quartet on ‘Yesterday’ (1965), the increasing use of additional instrument colour such as strings for ‘Eleanor Rigby’, brass on ‘Got To Get You Into My Life‘, ‘Yellow Submarine’ and ‘For No One’, a range of Indian instruments on ‘Love You To’ and ‘Tomorrow Never Knows’, the Hammond organ, coupled with the Leslie speaker (also used for guitars and vocals) on ‘Dr Robert’ and ‘Got To Get You Into My Life’, and the complex sound collages emerging in ‘Yellow Submarine’ and ‘Tomorrow Never Knows’, all contribute to a broadening of the Beatles soundscape. Although perhaps not a direct indicator of harmonic series content, it does however show us, in a more vertical sense, the ever widening awareness of the sonic space they could potentially inhabit as recording artists and not just as performing musicians, as the studio increasingly became the more important aspect of their music creation, reaching an apex in the orchestral climaxes of ‘A Day In The Life’ (1967) the following year.
Without going into a great deal of further detail, this essay can only hope to serve as the briefest of overviews to harmonic series content in what is after all, a considerable body of work. However, from this initial investigation, I would conclude that additional research will uncover further insights into the attraction of the harmonic series in not only the music of the Beatles, but other popular recording artists of the time and have implications for analysing spectral content in popular music in general.
Babuik, Andy. Beatles Gear: All the Fab Four’s instruments, from Stage to Studio. 2nd ed. San Francisco, USA: Backbeat Books, 2002.
Everett, Walter. The Beatles as Musicians: The Quarry Men through Rubber Soul. New York, NY, U.S.A.: Oxford University Press, 2001.
Everett, Walter. The Beatles as Musicians: Revolver through the Anthology. New York, NY, U.S.A.: Oxford University Press, 1999.
Johansson, K. J. The Harmonic Language of the Beatles. 1999. http://www.musikforskning.se/stmonline/vol_2/KGJO/Johansson.pdf (accessed April 5, 2013).
Lewisohn, Mark. The Complete Beatles Recording Sessions. London, UK: Hamlyn, 1988.
Mellers, Wilfrid. Twilight of the Gods: The Beatles in Retrospect. London, UK: Faber and Faber, 1976.
MacDonald, Ian. Revolution in the Head: The Beatles Records and the Sixties. London, UK: Pimlico, 1995.
Pedler, Dominic. The Songwriting Secrets of The Beatles. London, UK: Music Sales, 2003.
Platt, Peter. “Debussy and the Harmonic Series”. In Essays in honor of David Everett Tunley. Frank Calloway ed. Callaway International Resource Centre for Music Education, School of Music, University of Western Australia, 1995.
Pollack, Alan W. “Notes on ‘Tomorrow Never Knows’ “. Notes on … Series no. 194, 1995. The ‘Official’ rec.music.beatles Home Page (http://www.recmusicbeatles.com). (accessed May 23, 2013).
Riley, Tim. Tell Me Why: A Beatles Commentary. London, UK: Bodley Head, 1988.
Sheff, David. The Playboy Interviews With John Lennon and Yoko Ono. London, UK: St Martins Press,1981.
Tillekens, Ger. “A flood of flat-sevenths: Or, what are all those flat-sevenths doing in the Beatles’ Revolver?” In Every sound there is: the Beatles’ Revolver and the transformation of rock and roll, ed Reising, Russell. Aldershot, London, UK: Ashgate, 2002.
Valdez, Stephen. “Revolver as a pivotal art work: structure, harmony, and vocal harmonization.” In Every sound there is: the Beatles’ Revolver and the transformation of rock and roll, ed Reising, Russell. Aldershot, London, UK: Ashgate, 2002.