A [compressor](https://en.wikipedia.org/wiki/Dynamic_range_compression) plugin with adjustable settings. Introduced in LMMS 1.3.0-alpha releases.
While this page will show what each control surface does, it will not show you how to use a compressor. See [/pages/-LuIgsmdGe-oYxq2rFUT#id-7.1.3.2-compressor](https://docs.lmms.io/user-manual/effects/pages/-LuIgsmdGe-oYxq2rFUT#id-7.1.3.2-compressor "mention") for more information.
## Usage
The compressor in use using default settings
Looking at the effect window itself, there are two main components.
1. The background, which shows the compression curve, target, and input when audio passes through the effect
2. The control panel
### Controls
There are two sliders on each end of the panel, *In* and *Out* respectively. Each slider has their own volume control and L/R balance knobs.
It should be noted that the background curve will reflect the value of these controls in real-time, helping you visualize and measure what the compressor is doing.
* **MIX** controls how much compression is actually mixed into the wet output of the effect. Ranges from 0% to 100%
* The square headphone icon, when toggled on, allows the user to listen to the compressor's delta signal
* **THRESHOLD** controls the compression threshold. The effect uses *dBFS* as a unit of loudness. Ranges from -60 dBFS to 0 dBFS
* **RATIO** controls the compression ratio. Ranges from 1:1 to 20:1. Read on if you want to know how to make this into a brick-wall compressor with infinite ratio
* **ATTACK** controls the compressor's attack speed. The effect uses *ms* as a unit of time. Ranges from 0.005 ms to 250 ms
* The **AUTO** knob of the ATTACK knob controls the attack value based on the [crest factor](https://en.wikipedia.org/wiki/Crest_factor)
* **RELEASE** controls the compressor's release speed. Ranges from 1 ms to 2500 ms
* The **AUTO** knob of the RELEASE knob controls the attack value based on the crest factor
* **KNEE** controls the gain reduction curve around the threshold. Ranges from 0 db to 96 db
* **RANGE** controls the maximum gain reduction the compressor can perform. A higher RANGE value inversely affects the gain reduction. Ranges from -240 dBFS to 0 dBFS, which in theory would not perform any compression
* **LOOKAHEAD** controls the compressor's lookahead function when toggled on. It will introduce a flat 20 ms of latency regardless of the set lookahead length. When toggled on, the lookahead length knob ranges from 0 ms to 20 ms
* **FEEDBACK**, when toggled on, uses the compressor's output as the sidechain input
* *If LOOKAHEAD is enabled, FEEDBACK is disabled*
* **HOLD** controls the delay between attack and release stages. Ranges from 0 ms to 500 ms
* There is a toggle button that can switch the compressor's functionality from a **COMPRESSOR** to **∞ RATIO**. Infinite ratio on a compressor is called a brick-wall compressor, and functions more like a finely-adjustable limiter than a compressor
* **AUTO GAIN**, when toggled on, automatically adjusts the compressor's makeup gain based on THRESHOLD, KNEE, and RATIO
* There is a toggle button that can switch the compression channels between **LEFT/RIGHT** and **MID/SIDE** channels
* The **TILT FILTER** contains the tilt EQ settings of the compressor, the control group houses two knobs:
* **GAIN** controls the sidechain signal bias. -6 db is lowpass, 6 db is highpass. Ranges from -6 db to 6 db
* **FREQ** controls the frequency of the sidechain tilt filter
* There is a toggle button that can switch the compression source of the compressor between **RMS** compression and **PEAK** compression
* When using RMS compression, the **SIZE** knob controls the RMS buffer stored by the compressor
* **LINK BALANCE** controls the stereo balance of the output
* There is a toggle list of buttons that can switch the stereo link of the compression
* **UNLINKED** compresses each channel separately
* **MAXIMUM** compresses based on the loudest channel, this is the default
* **AVERAGE** compresses based on an average of both channels
* **MINIMUM** compresses based on the quietest channel
* **BLEND** uses a combination of the compression modes listed above controlled by the **BLEND AMOUNT** knob
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