Chorus, Flange, and Phase Pedals – What’s the Darned Difference?

In the dauntingly large and ever-growing domain of guitar stompboxes, chorus, flange, and phase effect pedals are not only extremely, er, effective, they’re also extremely popular. Now, while we’re all (allegedly!) very familiar with these three pedals, they can sound kinda similar on occasions. This is especially true when they’re used subtly — then it can often be a little tricky to identify exactly which one is being used, particularly the latter two.
I must admit, there’s been more than one occasion when I’ve thought a flange pedal was being used, only to discover it was actually a phaser — and vice-versa. As a result, there’s often more than a tad of confusion lurking when it comes to understanding exactly what each pedal is doing, how it’s done, and what’s the darned difference, anyway? Hence this article.
Let’s dive in to each of these three effects with the goal of hopefully clarifying any confusion that might exist — and don’t fret, we’ll be doing so in a “guitarist-friendly” (non-tech-head) way! Thanks to some of the “information” (I honestly feel that “misinformation” would often be a more apt description!) that exists on the Internet for all to see, the already murky water that surrounds these effects has been made even more muddy. So my goal with this piece is to try to make things a little clearer — without getting too deep and overly complex.
The three pedals we’re looking at here — chorus, flange, and phase — are all members of the modulation family of effects. So before we go any further, let’s define what “modulation” means.

What Is Modulation?
the exertion of a modifying or controlling influence on something.
When it comes to modulating sound, the definition gets more convoluted.
In nerdy, scientific/electronic terms, here’s what modulation means: “…the process of varying one or more properties of a periodic waveform, called the ‘carrier signal,’ with a modulating signal.”
Alrighty then! Dunno about you, but that’s not exactly 100% clear to me. So let’s simplify that confusing mouthful by saying this:
In a nutshell: “a modulation effect is one that messes with your guitar’s signal in a cyclical and desirable way. This not only adds a sense of movement to your sound but invariably adds musical width and dimension to it too.”
As we know, when used tastefully, chorus, flange, and phase can add extra life and a vibrant sparkle to a guitar part. And the same often goes for a less subtle use too. How are these desirable effects achieved? Well, in very simplistic terms, modulation pedals vary the frequency (pitch), amplitude (volume), or phase of your guitar’s signal in various clever and musically pleasing ways.
*Note: Phase is a pretty pivotal point for this particular piece. If you don’t fully understand phase, take a few minutes to read my article A Guitarist’s Guide to In and Out of Phase.
Based on these two definitions of modulation, in addition to the three we’re focusing on — chorus, phase and flange — other guitar effects that reside in this family would be tremolo, vibrato, rotary speaker emulation and ring modulators due to the cyclical nature of their audible impact on your sound.

Quick Detour: Tremolo & Vibrato: What’s the Darned Difference?
I’d like to quickly address the difference between tremolo and vibrato because, thanks largely to the legendary Fender Stratocaster guitar, these two types of modulation are a common cause for confusion, and understandably so. Thanks to the Strat’s so-called “tremolo bridge and bar,” confusion often reigns supreme here. Why? Because Fender’s naming is wrong here! Tremolo is the correct term for a modulation of volume not pitch! Vibrato is a modulation of pitch, and that’s what the so-called “tremolo bar and bridge” actually does when used — move the pitch of the strings up and down! So the Strat’s so-called “tremolo bar” is really a “vibrato bar.” End of story, and hopefully the end of any confusion too. In summary…

Tremolo = modulation of volume
Vibrato = modulation of pitch

To begin our discussion of chorus, flange, and phase, let’s go back in time (awful pun intended) — to a historical place where no flange, phase, or chorus pedals existed.
1. Flange

Flange pedals shown: Strymon Mobius, Electro-Harmonix Stereo Electric Mistress Flanger/Chorus, MXR EVH117 Eddie Van Halen Flanger, and BOSS BF-3 Flanger.

The Birth of Flanging
This effect can be incredibly dramatic — as proven by the main riffs of classic, hard-rocking cuts such as “Unchained” by Van Halen and “Barracuda” by Heart. There’s a couple of stories about how and when this effect was actually first created, and there’s also a cool story about how it was named and by whom.

Prior to the pedals we all know and love, flanging was created in those good ol’ analog recording studios using this 3-step process:

Record a song, or part of a song, on two separate tape recorders.
Rewind and cue the tapes to the exact same starting point, and hit play on both machines at the same time, then…
Alter the speed of one of the machines by pressing a finger against the outer flange (the protective rim: see figure 1) of the tape reel to slow it down a hair. This action puts the two machines out of sync due to the slight, random delay created by the finger’s pressure on the one machine’s flange compared to the other, “untouched” (awful pun, 110% intended!) machine.

Figure 1: The reel flange is the protective metal or plastic side of a reel.

The combination of these two signals causes peaks and valleys (created by the constructive and destructive interference that was discussed in the phase article) to occur at certain frequencies, and this continually varies (sweeps) as the playback of the two tape machines moves against each other. The resulting effect can go from a fairly subtle “wavy/swooshing” sound to a much more dramatic, “jet taking off”-type affair.
The random delay time (literally created via finger — a digit — in the pre-pedal days!) between the two signals that creates flanging typically ranges from 0.5 to 15 milliseconds, which is between extremely short and short! At the shorter end of this range, the delayed signal creates a filtering effect when combined with the original signal. At the longer end of the range, the mixture creates pitch effects (which is the essence of chorus — read on — hence the confusion that sometimes reigns). In technical speak, mixing a delayed version of a signal with itself results in something called comb filtering.
Diving a Little Deeper: Comb Filtering
This is a little nerdy, but I’ll try to keep it simple — basically so I can understand it! Here goes: a typical guitar signal is made up of a pretty complex blend of frequencies. When a slightly delayed version of that is mixed with the original, some frequencies will combine positively (reinforcing), while others will cancel (nulling). The resulting sequence of peaks and troughs (a.k.a. notches) from low to high frequencies (fig. 2) kinda looks like a comb — hence the term comb filtering.
And then, to top it off, modulating the delay time causes the comb filter to sweep through the signal’s frequency range, messing with different harmonics as it moves. And that, my friend, is flanging.

Figure 2: Comb filtering is aptly named, since the notches Look like a comb.

One of the first “big” songs to feature flanging was the 1967 Small Faces hit, “Itchycoo Park.” Listen to 0:50–1:09 & 1:50–2:09 to hear where the whole song is “flanged” — vocals, guitars, drums, the works!

Other artists who employed flanging creatively while recording during the ’60s included giants such as Jimi Hendrix and the Beatles. And talking of that mighty Merseyside quartet…
Flanging: What’s in a Name?
According to legend, the late, great John Lennon once asked the Beatles’ equally famous producer, George Martin, how this effect he liked so much was created. Apparently, Mr. Martin’s answer was a fairly flippant one that included the term “flange.” As a result, from that conversation on, Lennon always called it flanging. Fact or fiction, it’s a cool story!
While 1960s studio engineers definitely popularized flanging, apparently the creative genius Les Paul actually did it on a song called “Mamie’s Boogie” back in the mid 1940s! How did he create the effect? Well, according to a quote from the man himself (see Art Thompson’s excellent book Stompbox: A History of Guitar Fuzzes, Flangers, Phasers, Echoes & Wahs), he used a pair of disk recorders.
“I didn’t do it on tape,” the much-missed legend recounted. “You take two disks and start them out the same. I had one with a sync motor, which is 60 cycle sync, and the other was on an inductor motor where I could change the speed with a Variac [a variable autotransformer device that allows you to alter voltage]. I would start the two recorders together, and then I’d slow one down and speed it up ever so little.”
So now you know the backstory, or at least, how I heard it (© Mike Rowe of Dirty Jobs fame)!
How a Flanger Pedal Works
In short, a flanger pedal re-creates the “two tape machines and a finger” effect via a compact stompbox. It does it this way:

Splitting the original signal into two identical paths.
Delaying one of the signal paths ever so slightly (as already mentioned, typically somewhere between 0.5 and 15 milliseconds) and then…
Modulating this delay time (by cyclically speeding it up and slowing it down), then mix it back with the undelayed copy, creating the desired comb filtering effect we touched on a little earlier.

The result of this duplicates the random delay created by the manual (dare I say, “digital”? LOL) flanging done in the good ol’ days.
Typical Flanger Pedal Controls and What They Do
In addition to two fairly self-explanatory controls — rate (speed) and depth (a.k.a. width or range), some flanger pedals also have the following two controls:

Manual: this enables you to select the central frequency of the effect — from low to high as you rotate it clockwise.
Resonance (a.k.a. Regeneration or Intensity): this knob increases the intensity of the effect in an almost metallic fashion. It does so by feeding some of the delay being used back into the input. The reason it sounds metallic? Because the delay used in flanging is so short.

Geeky technical aside regarding the interaction between the width and manual controls: In a flange pedal, something called an LFO (low frequency oscillator) is used to replicate the varying delay times of good old-fashioned manual flanging. Technically speaking, a flange pedal’s width (range or depth) control sets the LFO’s amplitude (how much modulation), and the manual control sets its offset (where it occurs). What this means is as the width control is turned up, the manual control becomes less effective. Conversely, when width is set to minimum, the manual control is incredibly effective, allowing a full sweep of the entire delay range of the pedal.

Tone Tip: Unchaining Edward Van Halen’s famous “Unchained” flanger setting

The cool thing about having several controls on a pedal is the increased tweakability they allow you. The uncool thing is that too many controls can be confusing — kind of like a restaurant menu with so many main dish choices that you can never make up your mind!
As stated earlier, one of hard rock’s most iconic flanging moments occurs in the opening riff of Van Halen’s “Unchained,” and with good reason — when Edward engages the effect, it literally acts as a sonic turbo boost. The flange pedal he used to do this was an MXR.
Not surprisingly, MXR now offers the splendid EVH117 Eddie Van Halen Flanger, a pedal armed with four controls: Manual, Width, Speed & Regen. The 5150 dollar question, though, is this: what’s the exact “Unchained” setting? Fret not, my friend, if you’re looking for that exact sound, it’s incredibly easy to achieve. Why? Because the EVH117 features a handy-dandy button marked EVH that, when engaged (indicated by an LED — cool), instantly calls up that exact setting. Nice.

2. Phase

Phase pedals shown: MXR EVH Phase 90, BOSS PH-3 Phase Shifter, Electro-Harmonix Nano Small Stone Phase Shifter, MXR CSP101SL Script Phase 90, and EarthQuaker Devices Grand Orbiter V3 Phaser.

As previously mentioned, phasing and flanging are often confused due to how similar they can sometimes sound — especially when a phase pedal’s rate is set pretty slowly. The swooshing/swirling it creates makes the sound of the guitar appear to be moving away from you and then coming back again.
Some great examples of phasing in action are Led Zeppelin’s “The Rover,” Queen’s “Keep Yourself Alive,” and of course, Edward Van Halen’s epic “Eruption” — especially his highly lauded 2-handed-tapping finale. Another amazing and clever piece of subtle but incredibly effective phasing in action that’s not guitar related can be heard on John Bonham’s powerhouse drumming on Led Zep’s epic track “Kashmir.” Apparently, a rackmounted Eventide Clockworks PS101 was used to create this gem.
Phasing: Without Being Pedantic
The reason phasing and flanging are often confused is understandable because they are produced in a similar yet different way — if that’s not a classic example of an oxymoron in action! Let me explain:
The Similarity: Just like a flanger, a phase pedal splits the original signal into two, leaves one alone, but messes with the other, then mixes the two back together, and hey-presto: the desired effect is created.
The Difference: While both flange and phase pedals have a sweeping function (another similarity), the way these two sweeps are created is completely different. As we’ve already just learned, a flanger’s sweep is created by modulating the timing of the delay of the duplicate signal relative to the original one.
How a Phase Pedal Works

The signal is split into two identical paths.
One of the pair is left as is, while the other goes through a series of modulated all-pass filters, shifting its phase around certain frequencies.
The two signals — filtered and unfiltered — are then mixed back together, creating a series of notches that are swept up and down the frequency range by an LFO.
The rate of this sweep is determined by — wait for it — the pedal’s speed or rate knob.

The result? The gloriously pleasing, rise and fall swooshing sound we know and love as phasing. Figure 3 is a visual of the notches that a 2-stage or a 4-stage phaser would produce.

Figure 3: The number of notches a phase pedal creates is directly related to the number of all-pass filters (usually referred to as “stages”) it has. To be exact, two stages (filters) produce one notch. FYI, a phase pedal doesn’t necessarily need that many stages to sound great. For example, the benchmark MXR Phase 90 has four stages (two notches), while the MXR Phase 45 is merely a 2-stage (one notch) pedal.

To be honest, this is a pretty simplistic overview of how a phase pedal creates its magic. When you start digging, it can quickly get somewhat complicated and confusing. There’s definitely some gold out there in the digital domain, but as already stated, there’s also some stuff you’d rather not step in — so tread warily, amigo!
Phase 90 Fact 1
Edward Van Halen is synonymous with the MXR Phase 90 (the script logo version) — so much so that he now has his own red, black, and white striped signature MXR EVH Phase 90. The tale of how Mr. Van Halen got into using a Phase 90 is an interesting tale, so here goes.
Apparently, one of Edward’s guitar-playing pals in the early days played a lot of Robin Trower stuff and used an MXR Script Phase 90 to great effect when emulating Robin’s tone. He’d set the speed control to around 2 o’clock and get that trademark Trower fast swirl. So Ed got one, but as he didn’t play any Trower covers, he started messing with the speed control and found that setting it between 9 and 10 o’clock created a subtle but cool effect, which he still uses to this very day. He also discovered another advantage to using the pedal with this setting while playing lead.
“I did that in the early days because it would make the solo pop,” the legendary guitarist once told Guitar World. “Suddenly it became a different sound, which helped me stand out in the mix, because back in the club days, we usually had lousy PA systems and lousy sound guys. It didn’t boost the signal but it enhanced the tone and made it pop out so the solo was more audible.”
Since learning this, I’ve tried it, and it works — it’s definitely a cool little trick to have up your sleeve.
Phase 90 Fact 2
There are, in fact, two versions of the legendary MXR Phase 90 — the original script logo version (so-called because the MXR logo is written in, er, script!), born in 1974, and also the later, so-called “block logo” version — thus named because the MXR logo is — wait for it — in “block” text! Both are great Phase pedals but are not sonically identical. The Script version produces a slightly subtler, warmer, less pronounced effect, while the Block version is more in-your-face.
If you want the best of both worlds (unsubtle pun 100% intentional), then look no further than the MXR EVH Phase 90, as this has a button labeled Script that toggles between the two. For that trademark EVH tone, though, engage said Script button, set the speed somewhere between 9 and 10 o’clock, and then erupt!!

Four members of the MXR Phase 90 family, left to right:
Custom Shop, handwired reissue of the 1974 Script Phase 90, “Regular” Script Phase 90 with LED on/off indicator, “Regular” Block Phase 90 with LED on/off indicator, and
Eddie Van Halen EVH Phase 90.

And now, last but certainly not least, we come to:
3. Chorus

Chorus pedals shown: BOSS CH-1 Stereo Super Chorus, Electro-Harmonix Small Clone Analog Chorus, Catalinbread Callisto Chorus, MXR M234 Analog Chorus, MXR EVH 5150 Chorus, and TC Electronic Corona Chorus.

According to the dictionary, this is the definition of chorus:

Musica group of persons singing in unison.

We aren’t trying to make our guitar sound like a chorus of singers, but this pedal’s purpose is to make your single guitar sound like a group of axes playing in unison — just as its name suggests! And the good ones do a good job of this — a darned good job. A well-dialed-in chorus pedal can indeed thicken and colour your sound, adding sufficient depth, dimension, and richness to make it sound like there’s another guitar or four playing along in unison with you!
Again not surprisingly, as a result of this, chorus pedals are extremely popular — maybe not as popular as in the ’80s, but they still remain a strong seller. There are countless examples of a classic use of chorus on guitar, including “Come As You Are” by Nirvana, “Walking on the Moon” by the Police, “Welcome Home Sanitarium” by Metallica (the clean parts!), “Pretty Woman” by Van Halen, “I Will Follow” by U2, and of course, “More Than a Feeling” or pretty much anything by Boston!
Cool Historical Chorus Trivia
The first time chorus was introduced to guitarists was in 1975, when Roland unveiled the JC-120 combo — an iconic amp that is still a big seller over four decades later due to its benchmark clean tone. To many, part of the JC’s sonic charm is its built-in stereo chorus effect. JC, incidentally, is an acronym for Jazz Chorus.
Due to the incredible impact the JC-120’s chorus had on guitarists, Roland’s guitar effects division, BOSS, offered the same exact circuit in the CE-1 Chorus Ensemble stompbox a mere year later, in 1976. And the rest, as the saying goes, is history.
How a Chorus Pedal Works
To an extent, this is going to be yet another case of déjà vu due to the similarity between the way chorusing and flanging is created. There are differences, of course, but they are definitely pretty closely related — not just in the way they are formed, but occasionally sonically too. In fact, one of the artists considered synonymous with chorus is Andy Summers of the multi-platinum British pop band the Police. In truth, though — by Andy’s own admission — his early “chorus” sounds that are considered classic by many were actually created via a modified Electro-Harmonix Electric Mistress Flanger/Filter Matrix pedal. Trivia over, back to the main plot…
Basically, a chorus pedal does the following to create the desired effect:
The guitar’s signal is split into two: one of the signals is left alone, while the other signal is subjected to a short, cyclically modulated delay — sound familiar? When these signals are combined, the desired chorusing sound is created.
What happens is this: when the delay time of the one signal is increased, the converse occurs and its pitch drops relative.
You can hear said pitch-shifting happen if you twist the delay time control on a delay pedal back and forth while you’re playing — providing the pedal is “on,” of course! That said, the delay time increases and decreases that take place in a chorus pedal are very small and are cycled with perfect consistency too.
Chorus pedals that only use one delayed signal to create the effect are quite common. This sort of design is often called single voice. There are also chorus pedals that split the signal more than once, thus creating a multiple-voice chorus — an ensemble, if you will.
Now at this point, due to the aforementioned déjà vu, let’s quickly look at some of the differences between how flange and chorus pedals work.
The two biggest differences are these:

The delay times used in a chorus pedal are usually much longer than those used in a flanging device. Flange delay times typically sit somewhere in between 0.5 and 15 milliseconds, while chorus lurks in the 20ms to 50ms range. That’s a big difference.
Flange devices often employ positive feedback to intensify the effect, which is controlled by a knob (typically called regeneration or resonance), giving the effect an almost metallic-sounding, sweeping resonance. Chorus pedals don’t do that.

A Cautionary Chorus Concern
As cool as chorus pedals sound, if you’re too enthusiastic/heavy-handed with the Depth (and/or Level) control setting on certain pedals, the result can be a less-than-desirable “out of tune” sound. So always use your ears as well as your eyes when dialing in an unfamiliar chorus pedal — as wisely said in the classic Spinal Tap movie: “There’s a fine line between clever and stupid!”
What Is Static Chorus?
The first time I heard the term “static chorus” mentioned, I was a tad confused. Here’s the scoop.
Static chorus is when the aural illusion of there being more than one guitar is created by splitting the signal and using a subtle, fixed pitch shift (or two) via a harmonizer (or two!), as opposed to modulating the delayed signal(s) like a chorus pedal does. For example: a 3-way, “wet, dry, wet” sound setup with dry in the middle, a slight pitch shift of around +3 cents* on the left, and -3 cents on the right. This sort of setup will definitely widen your sound — and empty your wallet, as in addition to a harmonizer or two, you’ll also need three amps!
*Note: In harmonizer speak, a “cent” is 1/100 of a semitone, so it’s miniscule!
…and that’s all he wrote, folks! I don’t mind admitting, penning this one was a challenge, but an enjoyable and educational experience too.
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