Electronic Phasing and Modulation Effects in Psychedelic Classic Rock Music Production

G.L. Giustiniani - Honours Bachelor of Recording Arts - Middlesex Univeristy - SAE Amsterdam


The aim of this research is to investigate trends and practice of psychedelic and classic rock music production, in relation to the creative, technological, and psychoacoustic aspects of the use of effects known as Phaser, Flanger, Chorus, Vibe, Tremolo, Auto-Pan, Leslie rotary speaker simulator. The terms phasing and modulation of sound are explained more in depth in the following chapters, they are referred to periodic oscillations of phase, intensity, stereo panning, and pitch, generating, as a result, sensations of movement of the sound sources around the listener.
The hypothesis is that the use of such modulation effects has become the primary and indispensable production component in the psychedelic and progressive rock music genre, popular during the sixties and seventies, but, since then, established and still capturing nowadays considerable interest and following.
The author, as direct experimenter and composer, wants to demonstrate that the use of these effects is not only driven by the composer's intention, but also drives the very same composition flow, providing new and specific stimuli to the brain during the creative process. As shown from the conducted market investigation, this category of electronic gear has proven to be very popular and on demand in the audio field (Wilson 2008), thus originating the research question: what are the factors that make a modulation effect design become successful and possibly vintage over time, maintaining or even increasing its commercial and industrial value? Possible factors are to be found in quality and uniqueness of design, level of innovation, ability to stimulate composers creativity and listeners perception, and also the tendency of emulation or reference to the style of successful former artists who have been using that specific or similar gear in the past.
Electronic technology has always defined popular music during the last five decades, changing the role of musicians and engineers, creating new musical instruments, providing new sonic inspirations, opening the way to experimentation (Leeds 1997, Michie 2000, Braun 2002, Mason 2005). The seventies have undoubtedly been the years of the explosion of the new electronic tools dedicated to music production (Reid 2004, Thompson 2005), but the process has not stopped nowadays, finding a new powerful vehicle in Digital Signal Processing, sound modeling and emulation software plug-ins, and easy access to complex sound layering based on hard disk recording, as opposed to the laborious editing tasks once only possible on magnetic tape (Bode 1984, Clementi 1985).
The word "psychedelic" has been used in relation to music initially in the sixties and seventies to define the new experimental music era, influenced by chemically altered states of consciousness, making large use of new electronic effects, with extended layers of instrumental parts, giving rise to memorable productions in the history of popular music. This term, however, is not only used in music, but more generally is related to a particular state of mind that moves away from reality, in a dreamy atmosphere, and very imaginative mood, sometimes with the aid of drugs. In psychedelic music, perception is strongly stimulated and sometimes pushed to the limits by over emphasized and unrealistic sound effects, often associated to visuals, either actually provided through accompanying cover art or films, or simply described in the songs and induced to be imagined by the listener. The diffusion of the psychedelic music genre is heavily founded on the peculiarities of human psychoacoustics and emotiveness, upon which extensive scientific research has been done. It is not common, though, to find academic writings about the use of the mentioned modulation effects in music production, and their interaction with the human brain. The aim of the author is to attempt to establish a relation between the artists visions and inspirations, the sonic research, and the popularity of this gear on the market. The project follows these research methodology steps:
  • Study of previous literature on psychedelia and its interaction with music (Whiteley 1992 and 1997, Fachner 1999 and 2006, Blood and Zatorre 2001), psychoacoustics (Harris 1974), music composition in relation to the cultural and technological evolution of the last four decades (Théberge 1997).
  • Analysis of the market trends for such kind of gear within the music instruments business (Wilson 2008), to discover their past or present diffusion, manufacturing criteria, commercial penetration and perseverance. It includes technical reviews and practice opinions in the professional audio field (Riis 2003, Wilson 2004, Thompson 2005 and 2008, Taylor 2008), to understand what determines the success of specific equipment, adopted in live performances as well as in the recording studio.
  • Direct experimentation through the demo recording sessions of Sun Travellers' original compositions, conducted in Amsterdam, between 2006 and 2008, using the following effect modules: Moogerfooger Phasing, Moogerfooger Ring Modulator, Dynacord CLS-22 Leslie Simulator, Digitech RPM-1 Leslie Simulator, Digidesign Voce Spin Leslie Simulator, Ibanez UE-305 Stereo Chorus.

Psychedelia and Experimentation

The end of the sixties and the beginning of the seventies are a crucial and pioneering period for the rock music scene, defining the so called experimental progressive era. In those years the convergence of different aspects, such as the cultural revolution, the diffusion of the use of hallucinogenic drugs as expression of the counter culture, and the growing electronic technology applied to music affected substantially the artists creativity, inviting to push boundaries over previous canonical limits commonly accepted in popular music. Experimentation involved of course all forms of art, not only music, presenting new and unconventional canvases of styles, influenced from the changing social and political moods, as well as from the access to the new technological tools. In music, this is shown in the composition, where the typical form of song is often abandoned in favour of free-form instrumental parts, in the arrangements, now including electronic instruments, and in the sound design, making extensive use of effects and advanced mixing techniques.
Researching the biographies of some of the most famous bands of the underground scene that convoluted in progressive rock, like The Jimi Hendrix Experience (Jimi Hendrix 1973), Pink Floyd (The Making of Dark Side of the Moon 2003, Mason 2005), and Procol Harum (Michie 2000), shows how these musicians were often detached from conventional practices of songwriting and used to venture in direct experimentation during their live shows or recording studio sessions. An essential part of the creative compositional and writing process happened in the studio itself, where the sessions needed to be fairly extended in comparison with recordings of more traditional pop bands, due to the musicians often bringing undeveloped rough ideas, upon which they started improvising and assembling arrangements, largely influenced by adopting any new electronic gear available at the time (Black 2001, Daley 2007).
Introspection, mysticism, uncertainty, dislocation, confusion, blurry visions are the recognizable elements of underground music productions flourishing in the late sixties (Jones 1996), in many cases, but not necessarily, fueled by the consumption of hallucinogens, like LSD, or other chemicals inducing altered states of consciousness. Aldridge, Fachner, and Schmid (2006) describe altered states of consciousness as an attractive way of escape from the colourless routine of everyday life, the desire of distraction from the ordinary. In the early psychedelic era of the sixties, following the changing social and political climate, such a desire of renewal was elevated to an ideal of seeking and following alternatives in the way of thinking, judging, working and producing in many fields of human activities, with particular regards to creative arts, which, historically, have always been the primary vehicle for new cultural movements. The men and women of the psychedelic years are looking for new journeys, extraordinary experiences, spatial exploration, enhancement of perception. They dare to express what, until few years before, was considered non-expressible, and focus to adopt music and intoxication as the substantial aid to this emotional and cultural process (Whiteley 1997). Expanding and blurring the acoustic space is, metaphorically, enhancing visions, abandoning conventions, breaking down order into entropy in order to see what has not been seen yet. Particularly enthusiastic reactions among musicians and audio engineers were manifested after smoking cannabis, which proved to affect positively their auditory perception, in terms of better discernment of timbre, expansion of time, due to the own internal clock being perceived faster, increased sensitivity to volume dynamics and to sound effects (Fachner 1999 and 2006). Interviews conducted by Curry (1968) to drugs consumers between musicians and members of the audience in clubs and concerts during the sixties revealed pleasant effects in the musical experience, with hyper focused perception of sound, deeper consciousness and expansion of acoustic spaces. It is reasonable to believe that such obtained lower thresholds of sensitivity to sonic variations could successfully expand the mindset and inventiveness of the music practitioners under the effect of these drugs, probably inducing to process the sounds more accurately and with a greater number of effects than in normal conditions. It is then a sensible hypothesis that the overall process, when adequately controlled, must have been beneficial to music production, arousing major interest in the listener, and setting new standards for the time.
In the analysis of early compositions and arrangements from emerging rock acts of the mid sixties like Beatles, Cream, Jimi Hendrix, Pink Floyd, Whiteley (1992) developed the concept of “psychedelic coding” describing some common representative elements of psychedelic rock. These are surrealistic and dreamlike images expressed in the lyrics, when these are present, overlapped and distorted timbres that reflect the unfocused and sometimes sinister visions, unconventional guitar playing with large use of time based effects and feedback, sustained glissando, producing an indefinitely extended and continuous pitch shifting. At the same time, the alternating of heterogeneous moods and motifs within the same composition, defined the concept of progressive music, resulting, in fact, in open and evolving structures which allowed room for virtuoso improvisation by the lead instruments.

Sound research for psychotherapeutic applications (Leeds 1997, pp. 141-148) made practitioners and musicians aware of the powerful and diffusive effects of music and sound on the human psyche and nervous system. A composer or a producer with knowledge of psychoacoustics becomes a sonic alchemist with the power of driving perception, causing emotions and visions. Building certain kinds of tension, crescendo, or resolving relief in the music will result in a similar parallel internal process in the listener's psyche. In musical terms, if the aim is building suspense, the composition will probably play low frequency notes and sound effects, because the human brain will react to these frequencies with a sense of alarm, fear, and anxiety. Dramatic mood will be likely built upon minor chord passages delivered with sustain and presence, for the sense of sadness these particular interval progressions can generate. Differently, major scale progressions will tend to induce happiness and relief. A psychedelic, dreamy and multicoloured atmosphere will be rendered in music probably through progressions not following any specific interval rule, complex harmonies, at times dissonant or detuned, long and sustained notes, with large use of glissando and volume swells, mutating sounds (Rooksby 2001, pp. 40, 52).
Blood and Zatorre (2001) conducted a research among university students with a solid music background, in order to analyze emotions and physiological reactions induced by favourite music listening. The research surprisingly showed that a pleasant music experience activates regions of the brain known from previous studies as involved in euphoric responses to natural stimuli such as food, sex, and drugs. The scientists scanned brain blood flow patterns, measured skin temperature, electrodermal response, breathing and cardiac beat variations on the subjects while listening to their selected favourites, demonstrating that music caused excitement of brain structures associated with reward and emotions. This proves that music listening, although not a primary biological element of survival, is regarded to be a very powerful form of human addiction, potentially causing similar dependency as any chemical form, such as assuming alcohol or euphoriant drugs like cocaine. It should be said, though, music addiction must be certainly more beneficial than abusing drugs.
It is the author's hypothesis and direct experience that this highly uplifting effect is even more accentuated if the music listener is at the same time the music producer, for the deeper and pivotal involvement in such a creative process, most likely endeavoured to public distribution and popularity. The listening and perception process (Zacharov 2003) is triggered by the sound stimuli firstly causing a prime sensation, which is subject to an extent of variability in the physiologic sphere, possibly due to sensitivity and hearing abilities. The conscious perception is the next stage where the listeners use their cognitive factors to elaborate the sonic information. Aspects like association, memory, amount and quality of previous experiences are the elements that drive the way the stimuli will be interpreted, evoking diverse reactions, emotions, pleasant or unpleasant feelings that contribute to formulate a response, expressing the level of acceptance. Studying binaural hearing and spatial perception (Moulton 2005), it is clear that an auditory experience is always subjectively balanced between envelopment, intended as the perception of the sound ensemble all around the listener, with no definable point source, and localization, being the ability to identify where a particular sound is coming from, which leads to the recognition of the source. It is the natural mechanism of hearing, due to the differences in time, amplitude, and harmonic content of the sounds reaching the two separate ears, that allows to perceive directionality and ambience acoustics (Huber and Runstein 2005, pp. 62-66). For the so called Haas effect, whenever a sound is produced in an environment with any acoustic properties such as reverberation, even minimal, a fusion or combination between the original sound and the various reflections will occur for a limited time, approximately 35 milliseconds, during which the listener will perceive only one sound, fuller, louder, and richer of harmonics in accordance with the surrounding acoustic characteristics (Misner 1997, pp. 5-8). Reflections reaching the listener after that time will finally be perceived as distinct sounds, contributing to shape the idea of directionality of the sources. Harris (1974), in a comprehensive study of physiology of the nervous system, has pointed out some relevant aspects of the binaural perception of sounds generated by multiple simultaneous sources, modulated in frequency and phase. The reported experiments have shown that slight differences in frequency, like 3-6 Hertz, between two distinct sounds panned left and right, while not producing clearly perceivable beats, can lead the listener to perceive one single rougher and less definite sound, possibly shifting its location between the stereo channels, according to the fundamental frequencies and to their difference. This ensemble of motion and phase shifting (periodic variation within a range of values of the phase rotation angle between mixed soundwaves, through opportune filtering of the signal before being fed into the reverting circuit; Righini 1984) effects, more evident for tones or partials in the low-mid range of 400-800 Hertz, causes a sense of confusion in the perception of sound, due to the lack of definition and to the spatial dislocation, which is quite an interesting aspect to investigate for creative scopes. Interaural phase differences between the stereo panned sounds cause an effect of lateralization, similarly to an increase of intensity on the respective channel, however, modulating the phase can achieve much subtler movement effects than modulating the intensity. Such uncertain definition of sounds and equivocal directivity of the virtual sources contribute in detaching the listener from a sense of reality, but, being the phase modulation a cyclic effect, the dissociation is not ultimate and radical, but rather subdued and of varying intensity. Similar fluctuating effects can be obtained modulating the duration of a very short digital delay applied on the original tone with a low subsonic periodic signal of few Hertz. The delay needs to be well below 30 milliseconds, in order to not be perceived as a distinct echo, but as a blended enrichment of the original signal, and the modulating oscillation is normally tuned in depth and rate according to the music production directives.
Design and Technical Aspects

It is very common to hear audio professionals describe vintage sounds of the discrete electronics analog era as “fat” or “warm”, as opposed to “cold” digital sounds generated by the very large scale integrated components of the later years. What initially contributed to define the warmth of certain analog synthesizers of the seventies was, because of their proneness to detune, the particular fullness of sound when these instruments played together in unison, harmony, or double tracking (recording the same part twice on separate channels, to be panned generally left and right, slightly delayed each other within the Haas range, achieving the effect of spreading out and widening the sound), caused by slight discrepancies in pitch. These machines used to require continuous adjustments and careful voltage control of the power supply, working properly only within limited ranges of tolerance. The problem was solved with the advent of digital technology, but musicians also realized the loss of that peculiar aspect that actually characterized the electronic sounds of the seventies (Théberge 1997, pp. 207-212). The initially unwanted effects of detuning became very soon sought after by musicians and engineers, with the intent of expanding the sound, adding depth and atmosphere with additional multiple voices, delayed few milliseconds each other, and optionally modulated in intensity or panning, in other words implementing what today is called a chorus effect, which has become extremely popular as a standard patch present in any modern synthesizer.
The flanger effect also had a similar incidental origin, caused by an attempt of reproducing the same sound double tracked on two distinct tape machines, one of which failing to maintain the same constant speed (Bode 1984), causing a distinctive mix of distorted interference gradually modulating into a non-periodic phase shifting. Early phaser effects were also caused by presumably unwanted interferences between identical sounds slightly delayed each other, for example by an inaccurate positioning of microphones during recording. In this case the interference is alternately constructive and destructive following exact cycles, generating slight pulses and oscillations in volume and pitch.
All these sound alterations, initially discovered by mistake, but later adopted as creatively useful, are comparable with a guitar feedback generated by the amplified sound coming out of the speaker and returning into the amplification chain through the guitar pickups: if controlled, it can be superbly expressive for creative purposes. McSwain (2002) calls this process “reverse salient”, intended as a failure which is manipulated and newly conceptualized as a constructive and useful element for further development, particularly important here to remark once again the successful and influential outcomes of the sonic experimentation era.
Doubling, chorusing, flanging, and phasing are all results of the interference between the original sound and shortly delayed repetitions of it, within a maximum of 30-40 milliseconds, which, for the aforementioned Haas effect, is the limit after which the human brain will start perceiving distinct sounds instead of a unique and composite combination. What makes the sonic differences between these effects are the amount of delay, detune, and the modulation applied to these parameters through a low frequency oscillator, normally controllable in speed (also named rate) and width (also named depth, or range) (Misner 1997, pp. 29-32).
Martens and Marui (2006) conducted a listening experiment among young university students with computer science and audio background, in order to establish the best tuning range for pleasant musical effects provided by vibrato (pitch shifting), flanging, and chorus devices. The results placed the most effective and musically useful modulation depth on an average of 0.75 milliseconds, with the modulation rate varying between 2 and 9 Hertz. These settings are, in fact, within the range of the most common modulation devices available, mainly used on guitars or keyboards.
Any valid design of sound processors, today mostly based on digital delay circuits, simulating effects of moving sources through phase, pitch, and amplitude modulation keeps into consideration the principles of the Doppler effect. While the emitter source moves closer to the listener, it is still generating the original soundwave, causing its wavelength to reduce and consequently its pitch to increase, being these properties inversely proportional. As the source moves away from its nearest point to the listener, the emitted wavelength is expanding, causing instead its pitch to reduce (Abel, Berners, Serafin, Smith III, 2006).
History and Market

Before the design and diffusion of portable electronic devices like foot-pedals, mini-consoles or mini-racks, all effects which were desired in a recording had to be necessarily produced using the signal routes and controls available on the main mixing board, working with multiple tape machines, through the opportune placement of microphones at studied distances from the sound sources, and using calculated reverberation rooms when required. Clementi (1985, pp. 104-108) explains how, well before the days of console automation, engineers adopted mechanical linking devices to connect multiple potentiometers on adjacent channels of the mixing desk, in order to vary acoustic parameters like, for example, equalization, precisely and in accordance with the turning of one single panning knob. Through this system of mechanical linkage and synchronization between multiple knobs, and thanks to his knowledge of psychoacoustics, composer and engineer Giovanni Unterberger created an early and efficient method of simulating a sound source moving in circle around the listener, acting at the same time on the main channel stereo pan and treble controls, and on the treble controls of two routed auxiliary channels. The effect was based on the binaural principle for which sounds positioned in front of a listener are perceived with the maximum presence (emphasis of midrange frequencies specially audible by human ears, typically between 2000-4000 Hz), while a sensible loss of presence is detected when the same sounds are located behind the listener, with intermediate levels when sounds are positioned left or right.
Engineer Eddie Kramer, interviewed in Jimi Hendrix (1973) about working with the guitarist during the recording of the album Electric Ladyland, tells about a specific episode of Hendrix asking to reproduce on a recording the sense of daze and confusion he had experienced in a dream, where he had imagined to be surrounded by sounds and voices coming randomly from different angles around his head. Kramer explained how he successfully reproduced the effect from the mixing console, dynamically panning and modulating volume and delay of guitar and vocal tracks across the stereo field, resulting in a very captivating sound that fulfilled the artist's creative intention.
Composers and producers David Gilmour and Alan Parsons describe in The Making of Dark Side of the Moon (2003) the days when mixing a song, even once it was perfectly recorded, required an additional performance by musicians and engineers, who necessarily had to work with multiple hands on the console moving faders and controls in real time in order to achieve the expected results to cut the record. Nowadays, one single engineer can use a digital console and a mixing software like Pro Tools to easily build multiple layers of complex automation.
Before the explosion of the consumer electronics era, probably the most important electro-mechanical sound modifier invention, and later the most imitated, was the Leslie rotating speaker cabinet (Henricksen 1981). Originally created for the Hammond organ by Donald Leslie in 1941, but later extensively used on diverse lead parts, like vocals, guitars and synthesizers, it consists of two loudspeakers reproducing separately low and high frequencies, fed by two distinct amplifiers after a cross-over that splits the signal path from the preamplifier. The top driver is a rotating cone tweeter and the bottom one is a woofer surrounded by a coaxially rotating aperture. The resulting effect is an ensemble of amplitude and frequency modulation, due to the cyclic change of directionality and to the Doppler effect caused by the spinning cones, with the addition of acceleration and deceleration effects caused every time the the rotating speed is varied through the connected foot-pedal control. The pitch increase and decrease is more evidently caused by the tweeter rotation, and is very subtle and continuous (Abel, Berners, Serafin, Smith III, 2006).
As documented by Bode (1984), it is not before 1965 that the first ever portable effect for guitar appeared, that was the wah-wah by Vox, a powerful boosting peaking (with high Quality factor: a very high boost on a very narrow bandwidth; Huber and Runstein 2005, pp. 445-447) filter, with the centre frequency controllable by a pedal, being able to provide an expressive vowel tone modulation. Similar variable filters, though, had appeared already one year before on the first Moog modular synthesizer, together with envelope (attack, sustain, decay parameters; Huber and Runstein 2005, pp. 48-51) modification circuits. Electronic modulation effects saw the light only in the early seventies: the first flanger, designed by Eventide in 1973 and commercialized two years later; the first phase shifter, designed by Oberheim around 1968, and the Uni-Vibe multi-stage phaser, originally designed by Univox with the failed intent of emulating the Leslie rotating speaker system, but that actually became a distinctive effect of its own, loved and made popular by guitarists like Jimi Hendrix, Robin Trower, and David Gilmour (Riis 2003, Thompson 2008). Starting with the mid seventies, all major audio electronics brands invade the market with a number of modulation effects, in foot-pedal or rack layout, mostly tailored for guitar players. From Japan to United States: ADA, Boss, DOD, Electro-Harmonix, Ibanez, Morley, MXR, Roland, Univox, and many others release different models of phaser, flanger, and tremolo (oscillation of sound intensity, not to be confused with a vibrato which is an oscillation of pitch) effects, which quickly become essential in the gear equipment of any guitarist exploring the psychedelic or progressive rock scene (Reid 2004, Thompson 2005). Those brands are still manufacturing today reissues of the originals as well as new models. The fact that this particular kind of gear has become available in concomitance with the proliferation of the psychedelic and space rock acts demonstrates, in the author's opinion, the strict relation between this sort of technology and the musical style typical of progressive rock artists. These artists were demanding new versatile gear to experiment their new musical ideas, as well as to receive new inspirations, and the new gear needed to be portable to be used in live performances as effectively as in the studio. It was of historical importance for a lead performer to become able to apply a flanger or a phase shifter on a vocal or guitar part in real time and on the spot, instead of just figuring out how the same desired effect would have sounded when applied by the engineer at a later stage, necessarily requiring an intricate setup for double tracking on two tape machines, one of which tuned to play at a slightly different speed.
Signal processing effects have become essential in any musician's gear, market sales figures for the USA indicate that approximately 2,3 millions of units have been sold during the year 2006, for a total retail value of over 218 millions of US Dollars (Wilson 2007). This includes all kind of foot-pedals or rack-mounted multi-effect processors, but excludes software plug-in modules. The figures indicate that the number of sold outboard signal processors constitute approximately one sixth of all the sold fretted instruments, either classic or modern, in the same territory. They are certainly impressive, even considering the decreasing trend due to the expansion of computer based digital signal processors, such as Digidesign, Native Instruments, Waves, TC Electronic, available as software plug-ins for most of the mixing workstations today (Weiss 2007).
A research on the huge on-line marketplace, including the popular eBay, with over 60 millions of active registered accounts worldwide (Anon 2008), has revealed an increasing number of manufacturers developing new versions of modulation effects adopting renovated digital technology, or elaborating the original vintage analog projects with various customizations. Clones of the Uni-Vibe pedal from small scale US based high quality electronics brands, such as Fulltone, Moollon, Prescription Electronics, Sweet Sound Electronics, are offered for retail prices between US$ 250 and US$ 500 per unit, approximately one third of the average observed price for a rare second hand survivor of the original Shin-Ei/Univox version. Several other brands, like BBE, Danelectro, Digitech, Dunlop, Rocktron, producing in larger scale and with budget components, offer comparable units for more competitive prices, between US$ 100 and US$ 250. A similar scenario applies for the Leslie speaker simulators, very sought after items between guitarists and keyboardists, available in digital or analog versions from numerous manufacturers like Boss, Digitech, Dunlop, Hughes & Kettner, Korg, and many others (Anon, 1995, 2005). It is remarkable how these very specific modulation effects have become so popular to convince countless independent manufacturers to start producing replicas, being able to gain their own market share. It is clear how the success of these instruments has been established thanks to the reference artists who have been using them in the past. Those artists have built the standards that everybody now feels confident to adopt in countless reinterpretations.

Influential Productions

Of all the numerous classic rock productions showcasing brilliant use of modulation effects, the author has chosen some, mentioned chronologically, that have been particularly inspirational, innovative, representative of the psychedelic motifs, and achieving popularity and success.
One of the earliest experiments of flanging with two tape recorders is “Itchycoo Park” from Small Faces (1967), an upbeat single, transmitting an overall happy mood, suddenly interrupted by a variation in the chorus, where the rhythm section stops and the flanged vocals and cymbals switch into a quiet and introspective atmosphere.
Another example of flanging, in this case on the drums, can be listened to in the surreal “Have You Ever Been (To Electric Ladyland)” from The Jimi Hendrix Experience (1968), with, additionally, Hendrix guitar going through a Uni-Vibe rotary phaser, panned in stereo and continuously shifting between left and right.
The song “Planet Caravan” from Black Sabbath (1970), very essential in the arrangement, is a fascinating example of using a Leslie speaker in an unconventional way, in this case applied to Ozzy Osbourne's vocals, generating a blurry and dreamlike mood.
“Echoes”, from Pink Floyd (1971), is one of the most acclaimed psychedelic composition of all times, consisting of different moments merging different musical ideas in a long suite that originally took the whole B-side of the vinyl album. The hypnotic high piano note in the introduction is sent through a Leslie speaker and sets the surreal and spacey mood for the rest of the song. The mid section is probably the most evocative part, with plenty of remarkable sound effects reproducing natural elements. Particularly, David Gilmour's guitar fed into an inverted wah-wah pedal, which, in this configuration, behaves like a high-pitched oscillator, allowing modulation of intensity and frequency through the guitar's volume and the wah-wah filter itself. The result recalls shrieks and laughs of seagulls moving around the listener, with peerless use of stereo panning and time-based effects. In the closing verses, again some flanging on vocals, with the effect being pleasantly emphasized by the singing in harmony.
“Bridge of Sighs” from Robin Trower (1974), one of the most known references for the use of the Uni-Vibe phaser on guitar, with long and sustained bending, and additional hypnotic elements like the persistent cymbals, the pitch shifted triangle-like high percussion, and the pitch modulated wind effects.
Two songs from Camel (1976), “Spirit of the Water”, with the vocals being doubled across a clean channel and an additional channel going through rotating Leslie and probably flanging, and the romantic “Air Born”, containing profuse phasing effects on mostly all the lead parts of vocals and keyboards.
These productions have been more than influential in the later years, they have actually set new standards, both in the musical field and in the technological field. Musicians have been inspired for the innovative writing and arrangements, and manufacturers have been encouraged to produce new electronic gear attempting to replicate exactly the way those effects sounded.


A trancing state of mind can be induced in the brain by external stimuli, like chemicals, or internal factors, like, simply, thoughts or physiological agents. Music has been demonstrated to be one of the possible external stimuli inducing a state of trance. Particularly, music produced with sounds making use of modulation effects has a stronger power to achieve this result on a listener, because of the surrealistic sense of confusion and dislocation these shifting and swirling sounds can evoke.
There are of course subjective levels of predisposition among different listeners, that make one or the other more or less vulnerable to this psychedelic wave, but certainly sounds transformed with modulation effects have the power to increase the interest in the musical piece, because of the alterations they can generate in the state of mind.
The use of these effects in psychedelic music is planned at the same time of recording, in many cases introducing the effects in the signal path before reaching the multi-track recorder. This is important to understand how the modulation effects applied are essential part of the arrangement already at the time of composing, and attempts to prove that the link between psychedelic visions and sound modulation effects is inseparable, like words belonging to the same language. The composer does not simply need to embellish the sound using modulation effects, but to substantiate the creative journey itself, being the two, aspects of a unique state of mind.


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