Effected: Modulation

Whether it’s the watery, chiming open chords that start off The Dark Side of the Moon, that fat space ship landing tone of Unchained or those slick and powerful clean tones of Andy Summers on Police albums, Modulations are some of the most colorful effects in a modern guitarists arsenal.

Get to know LFOs

Although modulation effects are one of the most varied family of effects, they are all rooted in one thing.  They all use an LFO.  A Low Frequency Oscillator.  This is something that a synthesiser player is more readily familiar with than a guitarist but should be of interest to all players looking to get their tone to where they want it.
The sine wave an LFO emits is barely audible.  It’s use in many of these effects is to create a pulsing rhythm to effect a parameter like volume or pitch rather than produce it’s own sound..

Vibrato
Simply put, Vibrato is a rhythmic variation in pitch.  When you shake your guitar string you are really creating a rhythmic pulse of pitch change.  In an electronic effect, this is achieved by the LFOrhythmically making slight pitch changes to the guitar signal.

Vintage Uni-vibe vibrato

Tremolo
Tremolo takes the original signal and has the LFO create a rhythmic volume change.  These changes can be smooth like the wobbly chords in Money to far more aggressive, choppy tones.

EH Pulsar Stereo Tremolo

Flanging
The term Flanging came about due to the way this effect was first created in the studio.  The sound engineer would apply pressure to the flange or edge of a tape reel causing a slight delay.
In modern effect processor this is done by first splitting the signal into two.  One of the twin signals uses the LFO wave to rhythmically change delay times.  This is then added to the original signal.  During the delay changes, the signal go in and out of phase creating a wide range of harmonic effects.  
Depth controls adjust the mix of the two signals and rate adjusts the speed of the delay. 

Boss Flanger

Eddie Van Halen signature Phase 90

Phasing
Also called Phase Shifting, split the signal in two like flanging.  One signal is sent into an all pass filter, which inverts the phase of certain frequencies,  then through the LFO which rhythmically effects which frequencies are effected.  Then the whole mess is run parallel with the original signal.  Once again, how the two signals relate one another is the essence of the effect.
Depth is an adjustment of how far the frequencies get swept.  Speed controls the rate of the notches being swept. 

Chorus
Chorus is a very popular effect and for good reason.  It’s a tone thickener.  It mimics what truely happens when two sounds play at the same time.  It’s capable of really supporting your sound or create ambiant, dreamlike tones.  It’s the slight pitch modulations between the voices is what we hear as the chorus effect.  It is created similarly to Flanging but with a longer delay time and modulated pitch.  It starts with, again,  splitting the signal into 2 or more clones, treating all clones but one signal with an LFO rythmically changing pitch slightly, then change applying a delay of 2-30ms before mixing with the dry original tone.

MXR Chorus

Ring Modulation
Ring modulation is by far one of the strangest kinds of effects.  Famously used in space and horror soundtracks as well as all over early black sabbath albums, this effect has spent a long time on the fringe of popularity.  It uses an oscillator with an audible tone.  The oscillator gets multiplied with the guitar signal creating a third, unified  signal with a very complex harmonic structure.

EH Ring Thing is one of the most useful Ring Modulators

If you currently don’t own any modulation effects I highly recommend getting a multi-effects unit like the M9 by Line6.  It’s best to experiment and get to know these effects before you go out and drop some dough on an effect that isn't you. 

Line6 M9.  A one-stop effect shop.