What Are Vibrato Guitar Effects Pedals & How Do They Work?


Vibrato is an incredible technique for a guitarist, bassist, vocalist (and many other instrumentalists) to have in their arsenal. This natural technique can be achieved in both natural and unnatural ways via electronics in a vibrato pedal.

What are vibrato guitar effects pedals and how do they work? Vibrato pedals are stompbox-style effects units designed mainly for guitar and bass that electrically (via analog and/or digital means) produce vibrato in the audio signal. Vibrato is an audible variation in pitch of a musical note over time, defined by the speed and depth of the variation.

In this article, we’ll further our understanding of vibrato and vibrato pedals along with the other effects types that utilize pitch-variation in one manner or another. I’ll share a few pedal examples along the way and tips on how to get more out of your vibrato pedals.


Table Of Contents


What Is Vibrato?

Vibrato is a musical effect, often produced by vocalists and players of tuned instruments. The effects is that of regular pulsating variations in pitch, raising and lowering the pitch around a desired note.

Vibrato is used to give expression and character to melody lines and is largely determined by two factors:

  • The amount of pitch variation, or “depth”.
  • The speed at which the vibrato happens, or “rate”.

Singers can create vibrato via larynx control. String players can bend strings or bow the necks of their instrument (at the risk of going out of tuning or breaking something)! Brass and woodwind players can also achieve vibrato in various ways.

The above instances of vibrato are acoustic.

The vibrato effect can also be produced via electrical means. This is where vibrato pedals come into play.

I should note here that pitch is a subjective/perceptual property of sound (that translates into audio). The electronics (whether analog or digital) found in vibrato pedals, however, act objectively. This discrepancy is worth noting before we begin.

Musical pitch is a perceptual property of sound that allows listeners to qualify different sounds as being higher or lower in terms of musical notation. This auditory sensation allows us to relate the positions of different notes within the context of a musical melody.

Musical pitch and notation are related to frequency, though not entirely linked. The fundamental frequency (the lowest frequency of a note being played by a tuned instrument) is generally the most linked to musical pitch.

A note with a higher fundamental frequency will be higher in pitch. A note with a lower fundamental frequency will be lower in pitch.

The exact note value of a given pitch (with its fundamental frequency) is largely determined by the tuning system used.

In western music, the two most common tuning systems are 12-tone equal temperament with A4 = 440 Hz or A4 = 432 Hz

I’ve written about the relationship between pitch and frequency in my article Fundamental Frequencies Of Musical Notes In A=432 & A=440 Hz if you’d like to check that out.

Guitarists, I should go beyond the explanation above to state that vibrato is not tremolo and tremolo is not vibrato. Don’t let Fender fool you!

Tremolo is a rather fast modulation of a signal’s amplitude. Vibrato, as we’ve discussed, is a rather fast modulation of a signal’s “pitch”.

The “vibrato” effect built into some amplifiers (you, the one that varies the amplitude of the signal) is really tremolo.

The “tremolo arm” (sometimes referred to as the whammy bar) that affects the pitch of the guitar is really vibrato.

Labeling of tremolo and vibrato can become tricky in the world of guitar. It’s important, then, to not only know the true definitions of the two effects but also that you’ll likely run into improperly-labeled units during your lifetime.

To learn about tremolo pedals, check out my article What Are Tremolo Guitar Effects Pedals & How Do They Work?


What Are Vibrato Pedals & How Do They Work?

Vibrato pedals are stompbox-style units designed to receive guitar, bass or other instrument signals and emulate the vibrato effect by altering the characteristics of the audio signal.

These pedals work by modulating the frequency content of the audio signal in order to affect the perceived pitch of the signal when it is transduced into sound.

It’s important to note that, electrically speaking, vibrato pedals fit into the modulation category of pedals even though the audible effect is that of pitch-shifting. Pitch-shifting pedals are a bit different, as we’ll discuss later in this article.

The vast majority of analog vibrato pedals are designed essentially as delay pedals with no dry signal at the output; no feedback loop, and a low-frequency oscillator (LFO) that modulates the delay time of the delay circuit.

So while a simplified diagram of an analog delay pedal would look like this:

A vibrato circuit will do away with the feedback loop of the delay so that the delayed signal is not repeated.

…A simplified diagram of an analog vibrato pedal would look like this:

Of course, there’s much more to an analog delay (and, therefore, an analog vibrato) pedal than this general overview but this is a great starting point. Their bucket-brigade device delay chips and the signal conditioning circuits are worth knowing about.

To learn more about delay pedals, check out my article What Are Delay Pedals (Guitar Effects) & How Do They Work?

How does a delay circuit act to affect pitch and cause vibrato? If you’ve ever adjusted the delay time of an activated delay pedal, you’ve heard how a delay circuit can alter the pitch.

By modulating the delay time of a delay circuit, we can alter the perceived pitch of the audio signal. Think of this as a sort of electrical Doppler effect.

The amount of delay the input signal experiences in a vibrato pedal is modulated via a low-frequency oscillator (LFO). This causes variation in the wavelength and, therefore, frequency/harmonic content of the signal.

As the delay time slows down, the signal is effectively time stretched, lowering its frequency content and dropping its pitch.

Conversely, as the delay time speeds up, the signal is effectively time compressed, raising its frequency content and increasing its pitch.

Imagine modulating the delay speed back and forth very quickly but subtly. This is what an LFO does. Together, this system yields the vibrato effect!

Note that, in the system, there will be some amount of latency (actual delay) between the input signal and the output signal as the signal is processed by the delay circuit. Remember that the vibrato circuit is like a modulated delay without the dry signal.

Actually, if we dig a little deeper we see that a vibrato circuit is actually a chorus circuit with a single copy and without a direct output.

Chorus pedals delay one or more copies of the direct signal and very their delay times to produce one or more voices with slight vibrato that are mixed in with the dry/direct signal at the output.

Digital vibrato pedals emulate this same basic design with digital delay and DSP (digital signal processing).

Note that uni-vibe pedal, which offer chorus and vibrato settings, are actually multi-stage phaser pedals, though they work with the same “vibrato = wet signal only” and “chorus = dry + wet signal” design.

To learn more about chorus pedals, check out my article What Are Chorus Pedals (Guitar/Bass FX) & How Do They Work?


Vibrato Pedal Parameter Controls

Vibrato, as we’ve discussed, is largely defined by the speed and depth of the pitch oscillation. Let’s look at these parameters along with the other controls we’ll commonly find on a vibrato pedal:

Depth

Depth is the amount of pitch changing the vibrato effect will produce.

In other words, it determines the extent of which the LFO will control the change in delay time within the delay circuit.

Speed/Rate

The speed or rate parameter controls the frequency of the LFO and, therefore, the speed of the perceived pitch alterations.

Rise Time/Ramp

Rise time or ramp controls the initial onset of the vibrato effect once the pedal is engaged by ramping up the level of the LFO.

Mode

Mode can mean a few things.

Most often, it refers to the functionality of the pedal’s foot switch or, in other words, what the role of the foot switch will be for the pedal.

The Boss VB-2W Waza Craft (link to check the price on Amazon) has rate, depth, rise time, and mode controls. Its mode knob controls the functionality of the footswitch between latch, bypass and unlatch modes.

Latch mode means the pedal will be turned on with one click and bypassed with the next.

Unlatch mode means the pedal will be engaged when we step on the switch and bypassed as we step off.

Bypass mode is just like the latch mode except for one major difference: When the pedal is bypassed, the signal will bypass the analog BBD delay chip and will only run through the pedals’ buffered bypass circuit.

Boss VB-2W Waza Craft

The EarthQuaker Devices Aquaduct Vibrato (link to check the price on Amazon) has rate and depth controls. Its mode control alters the shape of the LFO rather than the functionality of the foot switch.

EarthQuaker Devices Aquaduct

Tone

Tone has little to do with the vibrato effect itself and instead activates either an EQ circuit; a boost, overdrive or distortion circuit, or some combination thereof.

The TC Electronic Shaker (link to check the price on Amazon) has the 4 controls mentioned above with the addition of a tone knob.

TC Electronic Shaker

Boss, EarthQuaker Devices and TC Electronic are all featured in My New Microphone’s Top 11 Best Guitar/Bass Effects Pedal Brands To Know & Use.


Tips On Using A Vibrato Pedal

Here are a few points to consider to help you get the most out of your vibrato pedal.

Subtlety Is Often Best

Vibrato is one of those effects that can get pretty wild pretty quickly. Unless you’re trying to make cartoon effects or something of the like, it’s likely best to keep the settings low.

That being said, in the practice room, I definitely recommend cranking the knobs to hear what happens. Perhaps you’ll find an awesome use for extreme vibrato!

Emulate Tape Warble

Combining vibrato with any type of lo-fi effect can yield some awesome effects. Keep the rate low and adjust the depth to ear.

Rise Time Can Be Your Best Friend

Natural vibrato is practically impossible to maintain consistently with acoustic instruments (including the voice).

Though we’ve largely become accustomed to the electronic vibrato effect, it can be to our benefit to make our vibrato pedals sound more “natural”.

Have a rise time will help us achieve this by offsetting the amount of vibrato the pedal will produce as we engage the pedal. This may require some clever pedal work (try using unlatched modes to get the most out of this technique).

Combine It With Tremolo

Combining vibrato with tremolo can add even more character to your sound by modulation both pitch and amplitude. Try it out for yourself with different rates between the two effects.


Where Should Vibrato Pedals Go In The Signal Chain?

Vibrato pedals, like most modulation-type effects pedals, work best after the dynamic, pitch-shifting, synth and gain-based effects and before the time-based effects (delay and reverb).

This often puts them near the end of the pedal chain, mixed in with phasers, flangers, choruses, uni-vibes, and the like.

Of course, this is just a suggestion. Try out different positions and listen for what sounds best to you when setting up the signal flow of your pedalboard!

To learn more about ordering pedals in the signal chain, check out my article How To Order Guitar/Bass Pedals (Ultimate Signal Flow Guide).


A Note On Pitch-Shifting Pedals

Although vibrato circuits have the effect of shifting the pitch of the signal up and down, they are actually a type of modulation pedal at the core of their design.

Pitch-shifting pedals, which are all digital, actually sample the signal and move its frequency content to a new “note”.

Older analog “pitch-shifters” are limited to monophonic octave addition.

Let’s now have a look at a few actual pitch-shifting pedal types:

Pitch-Bending Effect

Pitch-bending pedals bring time into the equation and can gradually shift the pitch of a note from one pitch to another. This can be done via an envelope, as we’ll see with the Boss PS-6, or via an expression pedal, as we’ll see with the DigiTech Whammy 5.

The Boss PS-6 (link to check the price on Amazon) is a harmonizer pedal at its core with octave capabilities along with key control; interval settings (including triads) and minor or major modes. As we’d expect the pedal also has a mix control to blend the direct and wet signals.

Boss PS-6

The DigiTech Whammy 5 (link to check the price on Amazon) is the modern version of the legendary Whammy pedal that started it all in terms of pitch-shifting guitar effects.

DigiTech Whammy 5

Transposition Effect

Transposition-type pedals act to transpose your entire instrument up or down in pitch.

The best example of a “transposition pedal” is the DigiTech Drop (link to check the price on Amazon).

DigiTech Drop

Detune Effect

Detune is an interesting effect. It is an effect that is sometimes included in pitch-shifting pedals (like the aforementioned DigiTech Whammy 5 and Boss PS-6).

What detune does is it duplicates the signal (as any pitch-shifter does) and alters its pitch by cents of a semitone (rather than by specified intervals).

The result is a thickening of the signal and a sound similar to a chorus pedal.

The DigiTech Bass Whammy (link to check the price on Amazon) has a “shallow” and “deep” detune setting. The extent of the detune is controlled via the built-in expression pedal.

DigiTech Bass Whammy

Octaves Effect

Octave pedals, as the name suggests, produce octaves above and/or below the determined pitch of the input signal.

The TC Electronic Sub ‘N’ Up (link to check the price on Amazon) is can produce the following octaves in addition to the direct signal:

  • 2 octaves below
  • 1 octave below
  • dry signal
  • 1 octave above
TC Electronic Sub ‘N’ Up

Harmonization Effect

Harmonizer pedals allow for much more than simple octaves above or below the dry signal. These digital pedals will typically offer the choice of several intervals above and/or below the note(s) of the input signal.

The TC Electronic Quintessence (link to check the price on Amazon) is a perfect example of an intelligent and versatile harmonizer pedal with preset and user-defined keys, modes and harmonies to choose from.

TC Electronic Quintessence

Shimmer Delay/Reverb Effect

Shimmer effects can be thought of a two-effects-in-one deal:

  • Shimmer delay is like a delay with a direct out and a wet/delayed signal that is pitched up via a pitch-shifter.
  • Shimmer reverb is like a reverb with a direct out and a wet/reverb signal that is pitched up via a pitch-shifter.

The Electro-Harmonix Canyon (link to check the price on Amazon) is a great example of a shimmer delay pedal, combining delay with pitch-shifting.

Electro-Harmonix Delay/Looper Pedal

The Strymon Big Sky (link to check the price on Amazon) is a great example of a digital delay pedal with tons of options.

It features the following emulations:

  • Room
  • Hall
  • Plate
  • Spring
  • Swell (a different take on the bloom-type reverb)
  • Bloom
  • Cloud (a cathedral-type reverb)
  • Chorale (a reverb combined with wah-like filtering)
  • Shimmer
  • Magneto (a reverb and delay effect emulating tape warble and echo)
  • Nonlinear (a non-linear, unnatural and programmable reverb)
  • Reflections (focuses on early reflections and sounds similar to a stereo delay)
Strymon Big Sky

For more information on delay and reverb pedals, check out the following My New Microphone articles respectively:
What Are Delay Pedals (Guitar Effects) & How Do They Work?
What Are Reverb Pedals (Guitar Effects) & How Do They Work?

Synth-Like Effect

True synth pedals are actually designed as synths with built-in oscillators that are simply controlled by an inputed guitar or bass signal.

However, some pedals are awarded the “synth” description if they simply sound like a synth. Pitch-shifting (particularly octave stacking) can turn a normal guitar signal into a synth-like audio signal. Combining that with other effects and filters can produce a sound that is more closely related to a synthesizer than a guitar.

The Electro-Harmonix POG2 (link to check the price on Amazon) is an example of such a pedal.

Electro-Harmonix POG2

To learn more about synth pedals, check out my article What Are Synth Pedals (Guitar/Bass FX) & How Do They Work?

DigiTech, Electro-Harmonix and Strymon are also featured in My New Microphone’s Top 11 Best Guitar/Bass Effects Pedal Brands To Know & Use.

To learn more about pitch-shifting pedals, check out my in-depth article What Are Pitch-Shifting Guitar Pedals & How Do They Work?


A Quick Discussion Of Frequency Modulation Synthesis

The vibrato effect modulates the frequency content of a signal with an LFO.

Low-frequency oscillators, as their name suggests, oscillate at low frequencies. Typically this means below 20 Hz (the lower limit of the audible spectrum).

What happens when we speed up the oscillation of a signal’s “vibrato”?

Well, the pitch oscillations would get faster and faster until we could no longer discern that the pitch is varying. This happens when we pass from the LFO range into the audible range.

At this point, the modulator signal (what would be the LFO) begins to shape the carrier signal (the audio) into a new waveform with different harmonic content.

The modulator still modulates the frequency of the signal but it alters the waveform rather than simply altering the perceived pitch.

This is the basis of frequency modulation, which, in the world of audio, is used in the following:

  • FM synthesis to create synthesized waveforms (the carrier wave is modulated by a modulator wave, typically in the audible range of frequencies).
  • FM radio transmission (where the carrier signal is in the very high frequency “VHF” band).

Here is a simple illustration of how frequency modulation works with sine waves:


What is the difference between tremolo and vibrato? Tremolo and vibrato are both time-varying modulation effects. The difference is that the tremolo effect modulates the amplitude (volume) of the signal while the vibrato effect modulates the frequency (pitch) of the signal. A “tremolo bar” on a guitar is confusing because it actually produces a vibrato effect.

What does a phaser pedal do? A phaser pedal is a stompbox unit that affects the input signal with a phaser circuit (analog or digital). The phaser effect utilizes an LFO to modulate multiple all-pass filters in series to sweep the phase of frequencies within the signal (or DSP that mimics this) to produce the phase-shifting effect known as phaser.

For more information on phaser pedals, check out my article What Are Phaser Pedals (Guitar/Bass FX) & How Do They Work?

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