Music is a gift that we all know and love… It’s a treasure worth more than gold, diamonds, and pearl combined. One can argue that the biggest power man has, is the power to create music. The success of creating quality music depends on many factors most of which must be handled with creative dexterity by the mix engineer to make a piece of music standout. If a mixing engineer does not combine these factors accurately, a poor body of music will be the only guaranteed result.
The most important factors that contribute to good quality music production are smooth volume control, audio compression, and equalization. Although all of the aforementioned are important, compression is still considered by many to be the most important tool necessary for achieving a good music production.
Compression in music entails an optimal reduction of the dynamic range of an audio production signal to eradicate unnatural sounds in the recording. The dynamic range in an audio production signal is the gap between the maximum and minimum loudness levels. Audio compression is very important to creating music of superb quality and the process involves an automated volume control that boosts the quiet part of the signal, and then attenuates the loud signals until the loud and quiet signals get even.
As rightly mentioned, compression is useful for sound production, recording, and reproduction of broadcasting, instrument amplifiers, and live sound reinforcement. The electronic hardware or audio software used for compressions are called compressors. In most Digital Audio Workstation software (DAWs), compressors are usually available as plugins.
Compressors are simple volume controllers which play a very important role in music production. A good compressor will have threshold, ratio, attack, release, as they are some of the parameters used in compressing music.
A lot of times, compression is usually confused as limiting. Compression and limiting may share similar processes, but they are not the same. The difference between them is in terms of their “degree and perceived effect.”
Let’s dive right into it!
Explaining the Compression Parameters
This is the level or point that must be exceeded by an audio signal before the compression process can take effect on the signal. For a compression process that is set at 2dB, the audio signal has to exceed 2dB before its compression will begin. The threshold is commonly set in decibels of dBFS (Decibel relative to Full Scale) for digital compressors, and dBU for hardware compressors. The lower the threshold level, the larger the portion of the signal that will be compressed, i.e., if I set my threshold to be at -40dB, it means it will compress any signal that’s above -40dB.
The ratio is the level at which an audio signal exceeds the set threshold before its output level can be increased. The ratio in compression tells us how much gain reduction is applied to the audio signal when the compression starts working. For every signal that goes over the threshold, it compresses to a certain level i.e., if the ratio set to the compressor is 4:1, the input signal will be higher than the threshold by 4dB before the output level can be increased by 1dB.
This is the rate at which the compressor works. When an audio signal exceeds the threshold, the compressor does not thrust the full weight of the compression on the overshooting signals, instead, the compression ratio is gradually allowed to increase until it reaches its peak within a certain time. The time it takes to compress an audio signal is called attack time.
Note: Compression with a ratio of 10:1 and above, with a fast attack time, is generally considered to be limiting and not compression. Limiters work by compressing in a high ratio albeit in a short attack time.
Release time is the time it takes for the signal to drop below the threshold. The compression does not immediately stop instead it is done in a gradual process till it gets to the ratio it was before compression takes place. As you may have guessed, a quick-release time will make the signal compression drop faster than a slow release time.
Make-up gain is the gain applied to an already compressed signal after the compression has taken place. This usually makes the compressed signal quieter than the original signal. The make-up gain allows the signal to be boosted so as to get an average volume for all signals.
Other parameters you may find in some compressor includes Soft Knee and Hard knee. Hard knee compression occurs when a signal is compressed immediately it exceeds the set threshold level while compression occurs in a gradual process in soft-knee compression.