Compression
A compressor turns the signal down once it passes the threshold. Ratio sets how hard. Attack and release set how quickly it grabs and lets go.
A compressor turns the signal down once it passes a level you set. The loud moments stop jumping out, and the quiet ones can sit nearer to them. The whole track gets quieter. Makeup gain puts the level back, so you can hear the compression itself and not just a softer fader.
The channel compressor, the Compressor, and Gravity share these controls.
| Threshold | The level where compression starts. Signal under it passes through. |
|---|---|
| Ratio | How hard it pushes back above that line. 2:1 is a light trim. 4:1 is obvious. Very high ratios behave like a limiter. |
| Knee | On devices that have it, how gradually the ratio takes over. A hard knee starts at the threshold. A soft knee eases in. |
| Attack | How quickly it reacts after the signal crosses the threshold. Slow lets the start of a hit through, which keeps a snare punchy. Fast catches that start too. |
| Release | How quickly it lets go once the signal falls back under the threshold. Very fast release pumps. Very slow release is still holding the next hit down. |
| Makeup gain | Boost after the compressor. Sometimes labelled Gain. |
| Peak | Reacts to instantaneous spikes. |
| RMS | Reacts to an average over a short window, closer to how loud the sound feels. On Gravity, an RMS window of 0 ms collapses that average to the first peak sample. |
Attack and release on an envelope are the shape of a note. Here they are how fast the level detector responds. Sidechain is the case where that detector listens to a different signal than the one it turns down.