What Is a Guitar Compressor?

by Alasdair Smith
A guitar compressor produces some of the more subtle electronic effects available.

A guitar compressor produces some of the more subtle electronic effects available.

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Electric guitar players often have an array of electronic wizardry through which they can manipulate the raw signal that comes from their guitars to produce a huge range of sometimes extreme tonal variations and sounds. A guitar compressor is one of the more basic foot pedal effects that most musicians will have in their arsenal for use during their performances.

Basic Function

The basic function of a guitar compressor is to reduce the difference between the strongest and weakest parts of the electronic signal coming from your guitar within parameters or a threshold set by the user. Compressors limit the loud signals and boost the low signals that are an inevitable result of the physics of guitar strings. In other words, as you play, your strings send out signals of varying strength, which the compressor will automatically compensate for to even out the tone. In this manner, by setting upper and lower thresholds to suit your instrument and playing style, you can produce a more consistent tone from your guitar.


Compressors were first used in studio settings, where their application helps recording engineers minimize distortion or interference from external radio sources. Compression in the studio is applied to all inputs, not just those from guitars, which helps engineers achieve a more balanced sound when mixing various inputs. Studio compressors are also more sophisticated devices, with a wider range of variable controls than is evident on the foot pedal versions used by guitarists.

Main Control Variables

The basic variables on simple guitar compressors, such as the MXR Dynacomp, are output volume and sensitivity. Output volume controls the level of the output once the signal has been processed while sensitivity controls the amount of compression, or softening. More sophisticated models from manufactures such as Boss and Behringer include additional controls to vary the level of adjustment to the high and low signals independently.

Using a Compressor

If you use a number of different foot pedals when playing live, it is essential to connect the compressor in the correct place in the chain of effects you use. For maximum effectiveness, the compressor should be the first unit you connect to from your guitar, before you connect to any distortion, overdrive or delay units. This ensures that all subsequent effects process a signal that has already been levelled according to your preferences.

Sound Effects

Compression adds sustain to the overall sound of your guitar solos, especially when playing a clean tone. It also helps to create a more fluid sound to lead guitar as heard in many country music solos. When used for rhythm playing, it creates a more consistent volume while when used with distortion effects in rock soloing it will fatten the sound.

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