Compressor 4

Name: Compressor 4
Price: 39.74 USD
Author: ToneBoosters

by ToneBoosters · Compressor · Zone-based mastering compressor

Not rated yet

Compressor 4 is ToneBoosters' mastering-grade compressor, with parallel, upward, downward and side-chain modes and a live display of levels and gain curves.

Its compression zones limit processing to chosen frequency and stereo regions, and it costs $39.74 (€35).

Best for: Mix Bus, Mastering, Vocals, Drums, Bass. Genres: all genres.

Keywords: mastering, sidechain input, bus processing, low latency, parallel processing, built-in analyzer, full mix, look-ahead, mid/side, transparent, bass, clean, drums, mix bus, built-in mix knob, mixing, single-band, upward compression, visual feedback, vocals, zero-latency.

What it does

Compressor 4 is a clean, general-purpose compressor that ToneBoosters calls a "mastering-grade dynamics processor". Its compression zones let it act on only part of the spectrum or the stereo field.

Core controls: threshold, ratio, makeup gain, range, knee, attack and release.
Compression modes: downward, upward, parallel (with a mix knob) and side-chain compression.
Compression zones: restrict compression to a chosen frequency region and to selected channels.
Stereo modes: left/right or mid/side processing.
Automatic timing: automatic lookahead and signal-adaptive release; with lookahead off it runs at zero latency.
Side-chain EQ: shape what the detector hears, with a spectrum analyzer to guide it.
Display and quality: real-time view of levels, spectra, gain reduction and curves; very low harmonic distortion and aliasing; up to 16 channels and 384 kHz.

Source: ToneBoosters product page

When to use it

Compressor 4 is a transparent, flexible compressor for people who want mastering-grade control without paying FabFilter prices. Compared with FabFilter Pro-C 3 it has fewer compressor styles, but its zone feature lets one band or channel be compressed without setting up a multiband plugin. It is more of a hands-on, all-purpose tool than TDR Kotelnikov, adding upward compression, M/S modes and a side-chain EQ with analyzer. Unlike Cytomic The Glue or Klanghelm MJUC, it doesn't model a specific analog unit, so it adds little color of its own.

Best for: transparent bus and mastering compression, upward compression, de-essing-style zone compression and side-chain ducking.
Genres: any style.
Look elsewhere if: you want the color of a vintage unit; The Glue or an 1176 or LA-2A emulation will suit better.

Where to buy

ToneBoosters: $39.74 (Listed at €35; converted at €1 = $1.1355 (ECB rate, 29 Sep 2026))

Tutorials and reviews

STOP! DON'T BUY ANOTHER COMPRESSOR UNTIL YOU'VE TRIED COMPRESSOR 4!

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