Compressor

Compressors were originally used to prevent a signal overloading an input, and indeed, compressors still are used for this purpose. In essence, a compressor is an automatic gain control: when a signal gets to a certain level the compressor restricts how much louder a signal can get.

Compression reduces the level of the loud sounds, but not the quiet ones, thus, the level can be raised to a point where the quiet sounds are more audible without the loud sounds being too loud. Contrast this with the complementary process of an expander, which performs almost the exact opposite function of a compressor, i.e. an expander increases the dynamic range of the audio signal.

In practice you're unlikely to want to use the compressor as a volume control and instead use it as an effect where it can help to:


 * make a sound fatter and/or smoother
 * enhance the perceived loudness of the sound
 * give the sound more punch

The disadvantages of using a compresor are that the resulting sound can tend to dominate a mix. With more extreme compressor settings, the sound will usually have a more uniform level and will fill a broader frequency range. Both of these factors can make it harder to mix a highly compressed synthesizer sound. Another downside of the compressor abuse is that the resulting sound tends to be less interesting - the delicate harmonic shifts of a patch tend to get covered up as all the harmonics take a similar level.