The voice that keeps disappearing
You are mixing a song and the vocal will not stay put. In the verse it sinks behind the guitars, in the chorus it jumps out on top. You push the fader up and the loud words start shouting; you pull it down and the soft words disappear. The problem is not the position of your fader but the distance between the softest and the loudest moment. That distance is called dynamics, and a fader cannot do anything about it: it moves soft and loud by the same amount.
A compressor can shrink that distance. It lowers the gain at the moments the signal rises above a threshold you choose, and leaves the rest alone. Afterwards you set what remains, as a whole, at the level you wanted.
Dynamics are not the same as loudness
This distinction carries the whole chapter. Dynamics are about the difference between levels within a signal, loudness about how loud something is in total. A compressor reduces that difference; by itself it makes nothing louder. That you can turn the result up afterwards is a consequence, not a property. Whoever confuses the two thinks that more compression brings more power, and only hears too late that the energy has actually drained away.
What you will learn in this chapter
- You use threshold, ratio, knee, attack, release and output gain with an understanding of what each control does.
- You distinguish peak control from envelope shaping, and consciously choose which of the two you need.
- You recognize the difference between macro dynamics and micro dynamics and treat them with different tools.
- You judge compression level-matched, so you hear what is happening instead of what is louder.
- You read the colors of compressor designs as tendencies instead of laws.
- You work with a repeatable method that works on every compressor, including an unfamiliar one.
Who this chapter is for
For anyone who mixes or produces and notices that individual elements do not stay stable in the mix. You do not need an expensive compressor: the built-in compressor of your DAW has the same controls as a classic unit. The chapter on EQ and masking is recommended prior knowledge but not required; concepts you are missing can be found in the free intro lessons of the earlier modules.
The core idea in one paragraph
A compressor is an automatic gain control. A detector measures the level, a calculation rule turns that measurement into gain reduction, and a gain stage carries out that reduction. Threshold, ratio and knee determine how much happens; attack and release determine when. The output gain puts the result back up to level and sits outside that measurement. In the next lessons you build this up: first the calculation rule, then time, then the goals, and finally honest judgment.