What Is A Modulation Pedal | An Introduction to Modulations

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What electric guitar’s pedals are considered modulations?

In the huge area of different types of effects, recognising a specific sound and fit each one into a specific category can be a great help in understanding better how the final sound of your electric guitar is actually made.

For this reason, in this article we’ll see a list of all the pedals that can be categorised in the area of effects that add that mysterious “modulation” to your signal chain.


A modulation pedal is a type of guitar effects pedal that allows the guitarist to modify the tone of their instrument: they change the sound of your electric guitar by adding a new layer to it, for example making it sound like it’s being played through an amplifier with rotating speakers, or adding a completely new behaviour to the soundwaves (for example rotating the soundwaves, like in the phasers, or adding a delay in the soundwaves, like in flanger models).

Modulation pedals are used for a variety of purposes, but they are most commonly used for creating sounds that don’t exist on an electric guitar by themselves, and they greatly enhance the possibilities of the guitar and also allows musicians to create sounds that are impossible with just their hands and fingers.


We can recognise 5 different types:

  • phaser;
  • flanger;
  • chorus;
  • tremolo;
  • vibrato

Effects processors manipulate the initial sound by either delaying it or changing its pitch, before blending the two wavesformed sounds together. This results in a series of peaks and notches with the shape of a waveform. Since the frequencies get more intense at certain points on the 360 degree axis, they can emphasize various frequencies throughout the cycle.

The differences made by those pedals can range in various types of changes to the original signal and the original soundwave:

  • they can change the pitch (the vibrato and also the chorus);
  • they can change the timing (for example the flanger that makes a copy of the soundwave and then delay the second of a few milliseconds, or a rate that can be changed through the settings);
  • they can mix the signals in a customisable way (the chorus, that mix the signals and changes the pitch);

After this general introduction, though, let’s see the main characteristics of each one.


Phasers work by shifting different frequencies out of phase with one another and inserting notches periodically at uniform intervals across frequencies. This creates a swooshing noise that gives your signal some liveliness and a very ambient-like sound.

Some famous models are the MXR Phase 90 (one of the first models, that shaped the industry for this kind of guitar effect and also being used by David Gilmour in Pink Floyd’s songs), the “Lilian” from Walrus Audio and the BOSS PH-3 Phase Shifter and the Electro-Harmonix Small Stone Nano.

Regarding to bands heavily using this type of modulation, we can quote the Pink Floyd, as David Gilmour experimented a lot with this, as well as Radiohead , Tame Impala and in general the genres of ambient guitar (but this last can be said for all modulations).

(you can also read more about phaser here)


This pedal works by splitting (in other terms, dividing) your input soundwave into two different parts and then one of these is altered by adding a slight delay (of a few milliseconds): in short, one of these remains the same soundwave and can be heard as soon as the signal comes to the effect pedal, but the other will be heard a bit later, giving that “echoed swoosh” sound when you play.

Some famous and popular models for this effect type are the BOSS “BF-3”, the Electro-Harmonix “Stereo Electric Mistress” or the MXR “EVH-117”.

Famous songs using this are:

  • “Heart” by Barracuda;
  • “The Spirit Of Radio” by Rush;
  • “Ain’t Talkin’ ‘Bout Love” by Van Halen, that also uses a delay for the famous main riff.


A chorus pedal is an effect that makes your playing to sound like if multiple instruments were playing at the same time, resulting in a lot of added depth in your own sound and rhythm/solos.

This is actually achieved by altering the pitch and timing of the dry signal (or anyway of the signal coming into the input of the stompbox), in a way that can be adjusted using the most common knobs on this type of effect, the rate and the depth of the modulation effect.

Basically, you’ve got your clean audio mixed with an modulating signal, that results in the sound pulsing at a high rate (actually, the behaviour of this pedal is very similar to tremolo, but in this case the pitch is continuosly altered slightly, while in the tremolo one the alteration affects the volume, not the actual pitch).

Some popular models are the BOSS “CE-2W Chorus”, the Walrus Audio’s “Julia”, the Electro-Harmonix “Neo Clone” and the TC Electronic “Afterglow” and “3rd Dimension”, while some famous songs with it are:

  • “Come as you are” and the verse of Smells Like Teen Spirit by Nirvana;
  • “Pull Me Under” by Dream Theater;
  • “Welcome Home (Sanitarium)” by Metallica;
  • “Purple Rain” by Prince;
  • also “Spirit of The Radio” by Rush (that used this effect in a lot of their song


Tremolo doesn’t actually change the pitch (as other pedals in this list do), but only the volume of your guitar sound, making it oscillate with a width usually chosen with the settings of the stompbox.

For this reason, some actually list this effect as an exception and not in the modulations.

Some models for this are the TC Electronic “Pipeline”, the Supro “Tremolo”, the Electro-Harmonix “Super Pulsar” and the Boss “TR-2”.

Famous songs:

  • “How soon is now” by The Smiths;
  • Introduction to “Boulevard of Broken Dreams” by Green Day;
  • “Bills” by Ultimate Painting;
  • the “oscillating sounds” from “Like a Stone” by Audioslave
  • “Money” by Pink Floyd


The vibrato can be defined as the oscillation of the pitch alone, without the dry signal combined with that modulation (we can say that it’s the modulation alone and the pitch variation on its own).

Some pedals of this type are the TC Electronic “Shaker” and the TC Electronic “Tailspin”, the Behringer “UV300”, the BOSS “Waza Craft VB-2W” and the Walrus Audio’s “Julianna”.

Some songs with this (despite it being often replaced live with the tremolo arm in the guitar, that in fact acts as a vibrato arm as it changes the pitch and not the volume like the “true” tremolo) are:

  • “Bridge of Sighs” by Robin Trower;
  • “Impossible Germany” by Wilco;
  • “Coffee and TV” during the solo, by Blur

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