Compression (kəmprɛ́šən) is an electronic method of leveling sound dynamics to a narrower range. Compressors bring up the signal of quiet passages and reduce the volume of loud passages according to the ratio and threshold and level settings for a more even, consistent volume output. There are times when the dynamic range, or the difference between the quietest and loudest notes of a guitarist’s playing, is too wide, making the music sound uneven. Rather than trying to increase and/or decrease the volume while playing, this difference adjusted is through compression.  

Guitarists will often use compression to get notes to sustain without distortion, by prolonging the decay of notes that are getting quieter. Country guitarists are known to use compression to achieve a clean sustain where the notes seem to pop out with each pick stroke. In funk guitar, compressors are used to achieve an “in your face” presence on recordings.