Mixing: Dynamics
A compressor is an automatic volume knob with a threshold. Above the threshold it turns the level down; below it, it lets go. That is the whole mechanism, and all the mystique around it comes from what attack and release do with that simple rule.
- threshold and ratio
- attack and release
- the character is in the timing
Where you run into this
- Mixing
- Production
- Live sound
- Mastering
In short
Threshold decides how often and how much the compressor works. Ratio decides how hard. Neither of them decides how it sounds. That is attack and release: attack sets how quickly the level is pulled down after a transient, and release sets how quickly it comes back.
Hearing a slow attack let the front of a snare through while flattening the tail is the moment compression becomes a tool rather than a setting.
How it works
A slow attack lets the transient pass and then clamps the body, which makes drums punchier. A fast attack catches the transient itself and makes them flatter and denser. A release that matches the tempo breathes with the track; one that does not pumps in a way you will notice for the rest of your life.
Where you run into this
- A snare that got punchier from a slower attack
- A vocal that sits in the track without ever being loud
- A mix that pumps because the release does not match the tempo
In practice
Realistic gain reduction is less than people expect: a few decibels on most sources, more on a vocal where two stages of gentle compression usually beat one aggressive one. If the meter is moving twelve decibels, ask whether you are fixing a performance problem with a plugin.