i'm trying to study for my A levels and struggling to understand the purpose of modulation? I'm getting the idea that it is simply something that enables a effects to change the timbre of a raw instrument?

So it allows you to add effects to a guitar or synth, etc...

Is this correct?

  • Modulation covers a lot of ground - in guitar terms, it generally refers to effects like flangers, phasers tremolo, vibrato and chorus. See e.g. musicradar.com/tuition/tech/…
    – jonrsharpe
    May 24, 2015 at 12:01
  • Okay so it pretty much combines audio signals to create sounds with unusual tonal properties. Thankyou for your comment :)
    – Macman119
    May 24, 2015 at 12:31
  • Not really, no.
    – user1044
    May 24, 2015 at 12:37
  • Please remove the tag modulation from your post as it refers to a whole different subject having to do with the change of keys in a score and not to the alteration of the timbre of a synthesized sound.
    – Chris
    May 24, 2015 at 19:03
  • 1
    Surely it refers to both?
    – Macman119
    May 25, 2015 at 18:05

2 Answers 2


Modulation is not an effect. Modulation is the process of varying one or more properties of something, in this case the sound of a guitar.

Effects are achieved through modulation (variation, change) of some property of the sound (like the phase, harmonics, frequency, amplitude, etc), but modulation itself is not an effect. This is very important to note to clear your confusion.

  • If you modulate the phase of a sound and mix that with the original signal you create the phaser effect.

  • If you modulate the time of a sound (using a delay) and mix that with the original signal you create the flanger effect.

  • If you modulate the amplitude (volume) of a sound you create the tremolo effect.

  • If you modulate the frequency (pitch, note) of a sound you create the vibrato effect.

  • Great! Thankyou! That has cleared up my confusion! My resources are a little confusing, but that makes sense :) Very helpful :)
    – Macman119
    May 24, 2015 at 15:05
  • Nicely put; clean & economical.
    – Tetsujin
    May 24, 2015 at 15:23

Modulation refers to an entire category of different effects that all have this in common: a dry audio signal is combined with another signal of the same sound that is delayed in time, slowed down or sped up. This makes use of the property that physics describes as interference or wave propagation. This creates phase cancellation and reinforcement. In most cases the degree of change in time itself is constantly and periodically changing, or being modulated. Hence the name "modulation" for this class of effects.

The classic modulation effect is the flanger. This sound was originally created by taking a tape recording of a musical instrument, making two copies of the tape, and loading it onto two different independent tape machines for playback. While one tape machine played back at a constant rate of speed, the second tape machine's speed was subtly slowed down and sped up in a periodic fashion by the engineer applying his thumb to the flange, or the outer perimeter, of the metal tape reel, to slow down and speed up the mechanism. The resulting sweeping sound was the result of the two tapes going in and out of phase with each other. Nowadays the same effect is achieved using analog or digital electronics, not recording tape.

Here is a YouTube video demostrating how the effect was originally achieved.

  • Okay so modulation refers to the process it takes to apply the different effects to a timbre? by combining a dry audio sound with different types of processes of modulation?
    – Macman119
    May 24, 2015 at 12:33
  • Yes i am currently revising all the effects. But what you are saying is that modulation just refers to a category of effects? So what "effects" would not be covered in modulation? Just so i can understand the difference between effects that aren't in this category?
    – Macman119
    May 24, 2015 at 12:44
  • Does modulation just cover any effect that changes the original audio signal by delaying it, amplifying it and changes it in any way?
    – Macman119
    May 24, 2015 at 12:46

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