Estimated reading time: 3 minutes

The compressor is one of the most important tools of the effects and mix chain: Level the dynamics, increases the sustain and makes the sound more coherent. In this article we see where to insert it in the chain, how to configure it, The main types of compressor and some open source plugins for Linux.

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Because it is important in the chain of effects

• Guitar pedalboard: often before of drives/modulations/environment, thus it levels the dynamics that will enter the subsequent pedals and increases the sustain without having to raise the gain.
• In mix: on single tracks (voce, guitar, basso), on buses (ad is. drums) and sometimes on the master for final cohesion.

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How to set it up correctly

Start with conservative settings, then refine by ear as you alternate bypass on/off.

Parameter	What does it do	Initial setting (guitar)	Note
Threshold	Level above which the signal is compressed	Adjust to make the GR work between 2–6 dB	Avoid excessive constant compressions
Ratio	Compression intensity	3:1 but a very strong manipulation on 4:1	Go up if you need more control
Attack	How quickly it kicks in	5–10 ms	Slower = more natural “attack” of the strumming
Release	How quickly it releases	50–100 ms	Adjust in time with the part played
Make-up Gain	Recover lost volume	Until the bypass level is equalised	Be careful not to saturate the next stage

Quick tip: look at the meter Gain Reduction (GR); working between 2–6 dB is often sufficient for rhythm guitar. For clean arpeggios and funk you can go up a little.

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Types of compressor and when to use them

Type	Character	Typical use
VCA	Necessary, fast, transparent	Bus, rhythm guitars, general control
Opto	Soft, musical, slower attack	Voices, clean guitars, dynamic parts
FET	Aggressive, colored, very quick	Electric guitars, drums, “punchy” sounds
Valvular	Heat, rich in harmonics	Bus/Master for sonic glue
Digital	Versatile, advanced functions	Any source; precise sidechain

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Practical examples

Pedalboard (clean/funk)

Catena: Chitarra → Compressore → Overdrive → Chorus/Phaser → Delay → Riverbero
Impostazioni: Threshold per 4–6 dB GR, Ratio 4:1, Attack 10 ms, Release 80 ms, Make-up per pareggiare.

Distorted rhythm guitar (mix)

Insert su traccia amp: Ratio 3:1, Attack 15 ms, Release 100 ms, GR 2–3 dB.
Obiettivo: compattare senza schiacciare l’attacco.

Sidechain on guitar with kick/bass

Key input: kick/bass → sidechain del compressore chitarra.
Riduci leggermente (1–2 dB) per far “respirare” la base ritmica.

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Plugin open source (Linux)

Plugin	Format	Strengths
Calf Compressor	LV2	Simple, intuitive; great for starting
LSP Compressor Suite	LV2/LADSPA	Various models, also multiband and advanced sidechain
ZamComp (About Audio)	LV2	Transparent, light, ideal on many tracks
x42-dynamics	LV2	Precise control, reliable on buses/tracks

Quick installation (Debian/Ubuntu):

sudo apt update
sudo apt install calf-plugins lsp-plugins-lv2 zam-plugins x42-plugins

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Klanghelm: the open source, but excellent

I would also like to mention the compressors as an outsider (plugin VST) Klanghelm. They are not open source, but the quality is really high. For those who want the full versions they can be found at very popular prices on the site, while in one section “freeware” are collected 4 plugins one better than the other: two compressors, a reverb and a saturator / distorsore.

Final advice

• Always confront compressor on/off a pari loudness.
• Look at the meter: if you see constant and high GR, you're exaggerating.
• Rule Attack/Release depending on musical time and of the genre.
• Use the compressor to check to dynamics, not to cancel it.

The compressor is a real one keystone of sound. From the live guitarist to the mixing engineer, learning to use it well is essential. On Linux there are excellent free plugins that don't make you regret commercial software and experiment with attack, release and ratio it is the best way to "educate the ear" and understand the dynamics of the signal.