How Do Modulation Effects Differ from Each Other?

With three main types of Modulation Effects, the differences can be confusing – our mini guide aims to de-mystify this

The three main modulation effects types are a staple of guitar pedal boards, and studio productions. Despite their widespread usage, there is often confusion over what chorus, flange and phaser do, and how each sound.

Read on, and we’ll illuminate how each effect works and how it sounds…

Modulation Effects - TC Vortex


The Beatles, as I’m sure you’re aware, were a rather creative bunch. Remarkably, they were even involved in the development of this effect. Credit for the ‘invention’ on the effect is given to Ken Townsend, an engineer at Abbey Road Studios.

As the legend goes, John Lennon was tired of double tracking vocals, and asked George Martin if there was any way of achieving the same effect artificially.

Townsend copied the vocal to a separate tape reel, and played it back with the original recording, but delayed it by fractions of a second, modulating its speed, by using a finger on the flange of the tape reel. John Lennon christened it ‘flanging’.

Modulation Effects - Boss BF-3 FlangerThe principles of a modern flanger effect are the same today as it was then. Essentially, the signal is split into two ‘copies’. One is then delayed, typically by no more than 20ms.

This signal is then modulated (varied in playback speed), and mixed with the original signal. A feedback control allows the user to adjust the amount of processed signal ‘fed-back’ into the effect.

The sound is harmonically complex, and can vary from subtle shimmer, to dramatic doppler-like ‘whooshing’ sounds.

Check out: Boss BF-3 Flanger, EHX Electric Mistress.


Modulation Effects - Dr. Tone Chorus pedalChorus works in a very similar manner to flange. The signal is split into multiple ‘copies’, with these copies delayed, then modulated in pitch, and mixed with the original.

Whilst the delays used on flangers are typically less than 20ms, chorus delays can be longer. In addition, chorus generally don’t allow feedback control.

Wide variations in chorus tone can be achieved by having different numbers of modulated signals, different delays, and different modulation speeds and depths. In many ways, this chorus modulation effects are far closer to the effect John Lennon was looking for, offering a sound that approximates to double tracking, or a chorus of different voices or sounds.

It ranges from a subtle, glimmering sonic shimmer, to rich, thick warm tone.

Check out: Boss CH-1 Super Chorus and Dr. Tone CHR-101 Chorus.


Modulation Effects - Boss PH-3 Phase shifter

On the surface, the phaser family appears to be a similar range of modulation effects to the flange family. There are certainly similarities.

Like the flanger, the signal is split into two identical copies. Unlike flange, the signal is not delayed. As the name suggests, the copied signal is put out of phase with the original, before being recombined at the end.

To understand how this works, you really need to understand a little bit about phase cancellation.

Looking at a sound wave, you can see peaks and troughs. If a trough (i.e. below the ‘zero’ line) combines with a peak (above the zero line), the resulting wave will be the ‘sum’. So, for example, if you have two sine waves that are fully out of phase with each other as below, the result will be silence.

Modulation Effects - Phase Cancellation

Varying this phase difference, as in a phaser, has the effect of cancelling and reinforcing different frequencies at different points. In addition, many phasers use multiple stages to create complex modulations, and often have feedback controls to adjust the intensity of the effect.

The result is a ‘wooshing’ sound similar to a flange effect, but far subtler.

Check out: Boss PH-3 Phase shifter, Jim Dunlop MXR Phase 95, MXR Phase 90.

So there we are. put simply, a chorus will give the most convincing ‘double-tracking’ type effects, and also add the subtlest, shimmery effects, whilst adding richness and warmth.

Both flanger and phaser add more dramatic ‘whoosh’ type modulation, with flanger providing the most extreme and complex of these.

For more information or to order any of the pedals mentioned here, call our stores or customer service team (01925 582420).