Compressors used to all be physical rack-mounted devices, but are most commonly used as software plugins like VSTs today. Compressors are super-useful devices for smoothing out volume spikes, giving quieter sounds more punch and presence. You’ll find a compressor on almost every main audio bus in a modern mix. They’re an indispensable part of recorded music. Learn to DJ with compression tricks by checking out some of the parameters you’ll find on your DJ program’s onboard compressor.
Attack and release parameters are concerned with the time during which the compressor is active. Changing the attack will change how quickly the compressor kicks in and begins reducing loudness. Both attack and release are measured in milliseconds (ms). An attack value of 0ms means that the compressor begins to work as soon as any incoming audio reaches the threshold. Low attack is good for punch in drum sounds. A higher attack value allows a certain small time interval before starting to work. This is good for vocals and organic sounds, which might sound unnatural if they’re too ‘instant’.
Release uses the same principle, but applies to the end of the incoming audio rather than the start. A release value of 0ms means that the compressor will stop working very suddenly. In fact, it will stop as soon as the audio dips below the threshold, and not a millisecond later. You might hear a noticeable dip in the sound level. This is useful as a way of cutting off drum and percussive sounds that do not need to linger in the mix after they’re done playing back. But at higher release values, the sound fades away more gently. Again, this is better for vocal and natural sounding instruments.
So, while threshold and ratio are concerned with volume (amplitude), attack and release are concerned with time. At 0ms, the signal would sound like a mute knob has been pushed. At higher values, it would sound like a volume knob has been turned down. How quickly depends on the value in milliseconds.
A knee is also a time control. It controls the suddenness with which the sound is compressed as it approaches the threshold. Like the attack value, it changes the start point of the audio by making it smoother or more sudden. But unlike attack, it actually anticipates the incoming audio, beginning to smooth it out even before the threshold is reached. A softer knee means a smoother sound while a harsher knee means more abrupt changes in volume as the sound dips and jumps around the threshold value. Make sense?
There’s plenty more to learn about DJing and using compression in your productions and performances. Make sure you get the right info from the pros by signing up for a DJ course online today.
John Bartmann is a music producer and DJ.