A compressor is a device that reduces (compresses) the dynamic range in a sound sources softest point to its loudest point to smooth the output, and can bring your audio material up to spec with professional recordings. An instrument that goes from very quiet and very loud over the course of a song can be difficult to record and mix. Either the quiet parts get lost or the loud sections overload the recording.
You can use a compressor to turn down the loud bits automatically, making the instrument easier to record or mix. You can also use compressors to make instruments sound fatter and bigger, and can be used to beef up vocals and to bulk out your finished mixes. Most audio professionals use compressors in every piece and sometimes on nearly every track in every piece.
Here are some features you may find on a compressor: Threshold - This is where you set the limits of the compressor, meaning at what level of dB do you want the compressor to start compressing. Using a setting near to zero would incorporate the compressor ever so slightly, if you want to add more compression set the levels to a more negative number. Attack - Attack basically refers to the speed at which you want the compressor to kick in. Do you want compressor instantly or would you prefer it to gradually phase in. Release - Once the compressor has kicked in, how fast or slow do you want the compressor to release and no longer compress the signal? Ratio - The ratio refers to how much the compressor is going to reduce the range of the signal. Gate - A gate is a device that will eliminate any room noise, making recording deadly silent.
It works by turning off the audio when it drops below a defined level. When the gate is open it simply lets any sound you plug into the input of the box straight through to the output. A closed gate doesn't let anything through - you just get silence on the output. When the sound at the input is below a certain level, known as the 'threshold' the gate remains shut. When the input goes above the threshold, the gate opens and the sound is carried through to the output.
Then when it drops back down again, the gate closes behind it. It can be used for example, to filter and eliminate any unwanted background noise. When you stop playing, and the sound drops below the threshold it will cut the sound to silence. A separate outboard compressor is a great tool to have as you can tame and level the sound source before it enters the computer. However there are of course drawbacks to this, once the sound is in the computer you will not be able to "uncompress" the sounds. Use the compressor moderately as too much compressor can drag the life out of your songs.
Overuse can result in all notes sounding the same and take away the dynamics of lighter and heavier notes.
Ian Marples has been playing guitar for over 10 years, and now runs the website http://www.uncleslinky.co.uk to help other guitarists learn how to succesfully record music at home. For similar information to this article subscribe to his FREE Newsletter by sending a blank email to homerecording@uncleslinky.co.uk
