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Some types of sound source such as certain instruments, by virtue of their construction or performance characteristics and human voices, are capable of producing a wide range of dynamics - for both very loud and soft sounds. During a recording session, the risk of unpredictable peaks when the signal is too loud or too quiet is an important factor.

Dynamic processors can greatly enhance the quality of mixes and songs. They manage these elements within fixed parameters so that they can be controlled within the mix. They act like automatic faders, riding the signal and either evening out unwanted peaks or remove some sounds entirely. They directly relate to a signal's perceived or relative loudness in the mix.


At the tracking stage the most basic use of a compressor is to function as an automatic volume control, reducing the fluctuations in level that are common when recording live instruments. For example, when a singer is moving around slightly, or an open chord on an acoustic guitar tending to be louder than a fretted one. In a digital recording system, there is a maximum signal level that can be recorded before the clipping occurs. This is referred to as zero decibels full scale (0 dBFS).

It is the peak volume level of a signal that determines how much gain can be applied before this 0 dBFS point is exceeded. Unfortunately, our ears are not very sensitive to the short, loud transients (such as drum beats) that create signal peaks, and it is actually the average signal level that our ears use to give us the impression of loudness or lack of it. Reducing the level of a signal's peaks allows you to apply more gain to the signal as a whole without causing clipping, and this in turn results in a higher average signal level, making it sound subjectively louder. (MacDonald, 2004)

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