1
FET Compressor Character
A compressor evens out a signal's loud and quiet moments. A FET compressor uses a field-effect transistor to do the gain reduction, and that circuit reacts extremely fast, so it catches sharp transients other designs miss. The speed gives it a punchy, aggressive character rather than a gentle one.
The best-known example is the 1176 style, and most plugin menus carry a FET-type compressor under some name. Reach for one when a source needs to sound more upfront: a vocal that needs presence, a snare or a guitar that needs attitude.
In practice: On a vocal, a FET compressor's fast attack clamps the loudest consonants and pushes the performance forward, often ahead of a slower compressor that smooths the rest.
FET = fast attack, punch and presence.
2
Optical Compressor Character
An optical compressor controls level with a light element shining on a photocell rather than a fast electronic circuit, so it reacts slowly and gently. The release depends on the programme: short peaks recover fast, sustained loud passages recover slowly. The result is smooth compression that flatters a performance instead of grabbing at it. Many optical designs have only two controls, peak reduction and gain.
The best-known example is the LA-2A style. Use an optical compressor when a source should sit more consistently without sounding processed: vocals, bass and acoustic guitar are its classic homes.
In practice: On a vocal, a few dB of peak reduction from an optical compressor levels the performance so gently that the listener does not hear the compression working.
Optical = slow, smooth, program-dependent levelling.
3
Serial Compression Technique
Serial compression splits the work between two compressors instead of overloading one. A common vocal chain puts a fast compressor (often a FET type) first to catch the sharp peaks, then a slower one (often an optical type) to smooth the overall level. Each does only a few dB.
Asking one compressor to do all of it tends to sound squashed; sharing the job across two tends to stay natural.
In practice: A vocal with whisper verses and belted choruses: a fast compressor catches the chorus peaks, a slow one levels the rest, controlled without flattening the emotion.
Fast comp catches peaks, slow comp smooths: split the work.
4
Parallel Compression (NY Compression)
Parallel compression, "New York" compression: blends a heavily compressed copy of a signal underneath the original dry signal. The dry signal keeps every natural transient and full dynamics; the crushed signal adds sustain, body, and density underneath.
The result is punch and consistency without the squashed sound: you raise the quiet parts without flattening the peaks.
In practice: An upright bass with great dynamics that vanishes in loud ensemble sections: blend a hard-compressed parallel copy underneath, the dry woody attack stays, the parallel fills the gaps.
Parallel compression blends a crushed copy under the dry signal, punch and sustain without squashing.
5
Parallel Compression Settings
The compressed signal in a parallel setup is meant to be extreme: a high ratio (8:1 to 20:1), fast attack, fast release. On its own it sounds crushed and lifeless, that is by design. The result comes from blending it low underneath the dry signal, typically 10-20%.
One pitfall: plugin latency on the parallel bus can phase-cancel against the dry signal (audible flanging). Enable delay compensation, or use the compressor's own mix knob to keep both signals in one plugin.
In practice: A parallel vocal bus sounding phasey and flanged: the compressor's latency is offset from the dry path, enable plugin delay compensation, or use the compressor's built-in mix knob instead.
Parallel compressors run extreme (high ratio, fast) and blend low, watch for latency phase issues.
6
The Volume Trick: Always A/B at Matched Level
Parallel processing always raises the overall level, because you are adding signal to the dry source. And our ears reliably hear louder as "better", so without level-matching, you will mistake the volume bump for an improvement.
The discipline: measure the output with and without the parallel signal, trim them to match, then A/B. If it does not sound better at matched level, it is not helping, you were hearing volume.
In practice: A mandolin that sounds "bigger and warmer" with parallel compression: measure the level rise, turn the dry signal up to match, then compare: keep it only if it still wins.
Parallel processing raises level, and louder fools the ear, always A/B at matched loudness.
7
Sidechain Compression: Beyond EDM Pumping
A normal compressor reduces gain based on its own input. A sidechain compressor reduces gain based on an external "key" signal you route into its sidechain input. So the bass can be ducked by the kick (not by itself), a synth pad can be ducked by the lead vocal, or a rhythm guitar can be ducked by the vocal, all without manual automation.
The sound people associate with sidechaining is the obvious EDM "pump", a heavy kick visibly ducking a synth bass every beat. That is one use. The far more common use across rock, country, pop, and acoustic mixes is subtle, inaudible-as-an-effect ducking: 1-3 dB of gain reduction on the bass when the kick hits, or on the rhythm guitars when the vocal enters, that clears space without the listener ever hearing the compressor work.
In practice: Country kick and bass masking each other in the 80-120 Hz range: route the kick to the bass compressor's sidechain, set 2-3:1 ratio with 1-3 dB of gain reduction. The bass ducks subtly on each kick hit, no pumping, just a tighter low end.
Sidechain = compressor triggered by an external key, for ducking frequency masks, not just for EDM pump.
8
Volume Automation vs Compression
Volume automation and compression both control dynamics, but at different timescales. Automation handles phrase-level moves, riding a quiet verse up, a loud chorus down. Compression handles note-level moves, evening out syllable-to-syllable variation.
Use both, in order: automate first to narrow the dynamic range to a manageable window, then compress gently to tighten what remains. A compressor alone cannot do the phrase-level job without crushing.
In practice: A folk vocal with a 15 dB verse-to-chorus swing crushed by a 4:1 compressor: automate verses up 6-8 dB and choruses down 3-4 dB first, then a gentle 2:1-3:1 compressor handles the rest.
Automation handles phrase-level dynamics, compression note-level: automate first, then compress.
9
Mix Bus Attack Time: Preserving Transients
A slow attack (10-30 ms) on the bus compressor is critical for acoustic music. It lets the initial transients, pick attacks, bow strokes, plucks, vocal consonants: pass through before the compressor engages, preserving the articulation and life of the instruments.
A fast attack catches and reduces those transients, flattening the mix. In bluegrass, the transients are the music.
In practice: A/B-ing 3 ms vs 30 ms attack: the 3 ms sounds "smoother" only because it is eating every pick and chop transient, choose 30 ms so the drive survives.
Slow bus-compressor attack (10-30 ms) lets transients through, fast attack flattens acoustic music.
These lessons are the teach side of knowledge cards from the Studio Mix deck. In the daily plan each one is followed by a quiz, spaced over weeks, so it stays known rather than read once.