Modulation audio effects are an important part of your mixing toolkit.

They’re the special way to add movement and groove to sounds that need a little something extra.

The main types of modulation are Tremolo, Ring Mod, Chorus, Phaser and Flanger.

Despite the different types, all modulation effects have something in common…

They all achieve their effect by modulating an aspect of the signal with an LFO (low frequency oscillator). The style of modulation is different depending on whether the LFO is manipulating the pitch, timing or volume of the signal.

Modulation LFOs work similarly to how LFOs are used in synthesis.

In this article I’ll go through all the common types of modulation, how they work and the best modulation plugins for each.

Tremolo

Tremolo is an amplitude modulation effect. Amplitude modulation plugins vary the volume of your signal.

It’s the easiest type of modulation to understand because you can easily hear the effect of the LFO settings on your sound.

A softer, rounded sine wave shape will create a gentle bobbing tremolo, while a steep square wave will create a machine gun stutter.

A softer, rounded sine wave shape will create a gentle bobbing tremolo, while a steep square wave will create a machine gun stutter.

Tremolo is commonly found on vintage guitar amps, so it’s associated with early guitar genres like surf and country.

But it can be a very interesting effect on all kinds of sources. Try using tremolo to create rhythmic action on sustained sources like synth pads or drones.

Best Tremolo VSTs

Free Plugin: Adam Monroe Tremolo

Adam Monroe’s Tremolo is an effective and easy-to-use vintage style tremolo.

Cheap Plugin: Goodhertz Trem Control

Goodhertz Trem Control is a great sounding, feature-rich tremolo that can go from subtle vintage vibe to experimental chop in an instant.

Pro Plugin: Soundtoys Tremolator

Soundtoys Tremolator is a fantastic creative tool for designing any kind of tremolo. Tremolator emulates some of the most classic hardware tremolo effects all in one powerful plugin.

Ring Mod

Ring Mod is basically an extreme application of tremolo. It uses the same amplitude modulation principle.

Ring Mod is basically an extreme application of tremolo. It uses the same amplitude modulation principle.

LFO frequencies used for tremolo are far below the range we can perceive as a distinct tone.

As you increase the LFO frequency into the audible range, additional tones called sidebands begin to develop in the signal.

The sidebands can be quite dissonant since they’re not evenly related to each other or the original sound.

This can result in some bizarre robotic effects and strange textures. Ring Mod is probably best known for creating the voices of the Daleks on Doctor Who.

Ring Mod is used significantly less than other types of modulation, so I’ll keep it simple for examples.

Best Ring Mod VSTs

Free Plugin: Melda MRingModulator

Cheap Plugin: Melda MRingModulatorMB

Melda MRingModulator and MRingModulatorMB are two great takes on ring mod from a quality plugin designer.

The basic version covers all of your traditional ring mod needs, while the MB edition includes sophisticated multiband processing.

Chorus

Chorus is another form of simple modulation. Chorus plugins make a copy of the signal and vary its pitch up and down.

Blending the dry and modulated signals gives a shimmery, detuned tone that can add depth and dimension to a sound.

If modulating a sound’s pitch with an LFO is ringing a bell, you’re on the right track. By using 100% of the modulated signal instead of blending it with the dry, you’ll get a vibrato effect,

Varying the characteristics of the LFO results in changes to the sound. Increasing the frequency of the LFO makes the rate faster while increasing the amplitude makes the depth more intense.

The first chorus effects created their modulated signals using analog bucket brigade device chips (BBDs).

These chips couldn’t copy the input signal perfectly, but the warm tone and fluid modulation they provided became a classic sound.

Best Chorus VSTs

Free Plugin: TAL-Chorus-LX

TAL-Chorus-LX is an accurate reproduction of the unique chorus found on the classic Roland Juno 60 synth.

Cheap Plugin: D16 Syntorus

D16 Syntorus is a versatile dual analog-style chorus. It offers complete control over each delay line for extremely precise chorus tones.

Pro Plugin: UAD Brigade Chorus

The UAD Brigade Chorus is an incredibly accurate emulation of the classic Boss CE-1 pedal. One of the first chorus effects on the market, the CE-1 is the pedal that started it all.

Phaser

A phaser is an effect that manipulates the phase of the signal with an LFO.

Imagine a sine wave on a graph. The phase is the starting position of the waveform along the x-axis expressed as an angle.

The phaser effect is created by splitting the signal and sending it through a series of “all-pass” filters that alter the phase.

The phaser effect is created by splitting the signal and sending it through a series of “all-pass” filters that alter the phase.

When the dry and phase-shifted signals are combined, any frequencies that are inverted 180 degrees cancel out, resulting in the characteristic notches.

As the LFO sweeps, notches will appear at different frequencies. Each all-pass “stage” introduces more notches into the sound.

This creates the churning frequency shifting character of phaser effects.

Best Phaser VSTs

Free Plugin: Blue Cat Phaser

Blue Cat Phaser is a free high quality phaser plugin that’s capable and versatile considering it’s free…

Cheap Plugin: D16 Fazortan2

D16 Fazortan is another entry into the series of highly flexible modulation effects from D16. This phaser has two LFOs available for more tweakability.

This phaser has two LFOs available for more tweakability.

Pro Plugin: Soundtoys PhaseMistress

Soundtoys PhaseMistress is one of the best sounding and most in-depth phaser plugins available. If you can’t get your perfect phase with this super-flexible plugin, it probably doesn’t exist.

Flanger

Flanger is the original modulation effect. It’s the recognizable “jet engine taking off” sound.

The first flanging was created with two tape machines playing identical tracks at the same time.

Applying pressure to the edge of the reel (or “flange”) of one machine would cause it to slow down and play back out of sync.

Flanger is the original modulation effect. It’s the recognizable “jet engine taking off” sound.

Summing the two signals together created the distinctive comb filtering sound that started to appear on recordings in the psychedelic 60’s.

LFOs are used to modulate the delay time in place of manually slowing down the tape in today’s flangers.

Flangers sometimes also include a “feedback” or “regen” control to mix some of the affected signal back to to the input to intensify the effect even more.

They’re great for thickening and stereo widening as well as that classic jet plane sound.

Best Flanger VSTs

Free Plugin: Blue Cat Flanger

Blue Cat Flanger is another great free option from a respected plugin maker.

Cheap Plugin: Toneboosters Reel Bus 4

Toneboosters Reel Bus 4 is an incredible bargain for such a full-featured plugin. In addition to great tape saturation emulation, it features a fantastic sounding tape flanger.

Pro Plugin: Softube Fix Flanger and Doubler

Softube Fix Flanger and Doubler was designed in collaboration with Paul Wolff, who engineered the original hardware BBD flanger in the 70s. The resulting plugin is a drool-worthy high-end flanger.

All Mod Cons

Modulation effects can be some of the most fun processing you apply in your mix.

Any of these modulation types can add movement, interest and dimension to your tracks.

To recap…

The 15 Best Modulation VSTs

Now that you know some of the best plugins for every modulation style, Start adding LFO action to your tracks.

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