Demolishing The Myths Of Compression

Compressors… 99% of us use them and most of us have a solidunderstanding of what they do, when and how to use them, and, critically, how to get what we need from them. But I’m going to make the bold assertion that very few of us truly understand how they work and exactly what all those controls do on a technical level – and that includes some of the people who design and manufacture hardware and software compressors.

This lack of understanding isn’t helped by a number of myths about how compressors work and how the controls on the front panel are able to do what they do which are perpetuated by bloggers, forum posters – even books and magazines.

This month I’m going to look at a handful of the most common myths.

  • Myth #1: Attack is the time it takes for a compressor to begin compressing once a signal crosses over the threshold

This may be my favorite audio myth of all time, because I think it’s the most pervasive. People who know a lot of things; people who’ve written books on the subject of recording and processing audio, have perpetuated this myth by writing about it, repeating it and passing it along as established fact so that you can read it passed off as fact in countless blogs and forums.

The only problem is that it’s completely, utterly incorrect.

And so, in the pursuit of truth, justice, and all that is good in the world, I give you the correct definition of attack:

Attack is the length of time it takes a compressor to apply roughly two-thirds of the targeted amount of gain reduction.

I say ‘roughly two-thirds’ because there is no agreed-upon, industry-accepted standard for what this spec actually is. Yes, you read that right: no two compressor designers will agree on exactly how to define, and therefore measure, attack. My definition above is within the ballpark of most thinking, so I’m running with it.

To understand this definition of attack better, you need to get some basics of compression established first. Let’s say your compressor is set with a threshold of -10dB and a ratio of 3:1. If you feed this compressor a signal at -11dB, nothing happens because the signal is lower than the -10dB threshold.

But if that signal jumps to -1dB things get interesting. Most notably, the instant the signal reaches -10dB the compressor begins attacking it. There is no delay whatsoever in this response, which belies the myth that attack is the time it takes a compressor to respond once a signal crosses

With a -1dB signal and a -10dB threshold, the signal is 9dB over threshold. Our 3:1 ratio means that for every 3dB coming in over threshold, the comp wants to allow 1dB out the backside. Since our example has a signal 9dB over threshold, our hypothetical 3:1 comp wants to compress those incoming 9dB into 3dB at the output, which would require 6dB of gain reduction.

Given that attack is the time it takes a compressor to apply roughly 2/3 of the targeted gain reduction, the attack in this case indicates how fast the comp will apply the first 4dB of the target 6dB of reduction.

If you don’t follow the math of this illustration, don’t worry. For now it’s enough to know that the compressor starts applying gain reduction as soon as the signal crosses the threshold. Which means that attack is not a delay before action, nor is it even a measurement of time per se; instead, it is a rate, a measurement of the speed at which the process of gain reduction is occurring.

  • Myth #2: Release is the time it takes a compressor to release
    compression after the signal drops below threshold

Without going into detail, let me just say that the above definition is not only incorrect – it would actually be an impossible thing to assign a single value to. (Which is a story for another column.)

The correct definition of release will come as no surprise given what you’ve read above:

Release is the time it takes a compressor to restore two-thirds of the reduced gain to the compressed signal.

‘Restoring reduced gain’ is a very carefully chosen set of words. I characterised release in those terms because it’s useful to think of compression as a two-way street.

When a compressor attacks, it is applying gain reduction – it is lowering the signal level.

But gain reduction is only half the picture, because for every dB of gain a compressor takes away, at some point it has to put it back. And that process – let’s call it ‘gain restoration’ – is the business of release. The faster your release, the faster the compressor restores the gain it took away when attacking.

So what do we know now, at least in a purely academic way?

Attack is the length of time it takes a compressor to apply roughly two-thirds of the targeted gain reduction.

Release is the length of time it takes a compressor to restore roughly two-thirds of that reduced gain.

This gives us a good grounding to tackle more compression myths.

  • Myth #3: A compressor won’t release until the signal drops below the

If you’ve been paying attention, it should already be obvious why this statement is false. The explanation lies in the fact that aside from generating ancillary effects like distortion and colouration from transformers and tubes, attacking and releasing a signal are the only two things a compressor can do.

Put a little differently: any time the gain reduction meter on a compressor is moving, it is either attacking or releasing the signal.

Fascinating! Taking it a step further:

Any time the gain reduction meter is increasing (i.e., the comp is reducing the gain of the signal), the compressor is attacking.

Any time the gain reduction meter is decreasing (i.e., the comp is restoring the gain of the signal), the compressor is releasing.

So while the well-intentioned myth-spreaders out there would have you believe that attack and release are only relevant when a signal crosses the threshold – attack on the way up and release on the way down – what I am telling you is that nothing could be further from the truth.

Instead, once a signal is over the threshold, both attack and release are constantly at play.

There’s a simple way to confirm this. Feed a drum loop into a compressor and set it up so that the signal is always over threshold and the gain reduction meter is dancing between say 6 and 12dB of
reduction. In this instance the compressor is constantly attacking and releasing the signal, as indicated by the dance of the meter.

If the myths were true – if attack only happened when a signal crosses above threshold, and release only happened when a signal drops below threshold – adjusting the attack and release knobs in the above scenario wouldn’t make any difference because the signal is perpetually
over the threshold … but turn the attack and release knobs and you will very clearly hear the sound of the continuous compression changing. Give it a try.

I think most people who use compressors on a regular basis already understand the above on an intuitive level, but some never make the connection that the behaviors they’re hearing (and seeing on the meters) don’t comport with the conventional – and flawed – wisdom.

  • Myth #4: Compression reduces dynamic range

How many times have you read this particular nugget of wisdom? And sometimes it’s true. But not always. Indeed sometimes it’s important that it’s not true.

Imagine a mix in which kick, snare, and cymbals/overheads feed a drum bus. The intuitive thinking goes something like this: if I slap a compressor on this bus and compress it, by definition I’m going to be pushing down the loudest stuff and as a result the dynamic range will be reduced. That’s what compression does, right?

Yes, and no.

Yes, a compressor can and does push down on the loudest stuff. But no, that doesn’t mean the dynamic range is automatically reduced, and here’s why: if your attack is slow enough, the loudest bit of that transient will come screaming through before the detector tells the gain circuit ‘TURN IT DOWN! Then, if your threshold is low enough and your ratio is high enough, what does get pushed down gets pushed down so far that the resulting signal is much quieter than it would have been if you hadn’t compressed it at all.

The result of those two factors: the loud stuff is just as loud (albeit for a shorter time) and the quiet stuff is quieter. Which is to say that your dynamic range is now increased as a result of the way you applied the compression.

Engineers exploit this reality every day on their drum buses; the classic trick is to take a comp set to a medium or high ratio, slowest attack, fastest release and dig in hard. With a deft set of
hands and ears, the result is a track that, on its own, is an unusable series of fast, dead-sounding thumps and pops that herald each drum hit in a highly exaggerated but uniformly level manner. This track is then blended in parallel, usually quite subtly, and the result is a palpable increase in the perceived impact, punch, warmth, and consistency of the drum sound.

So yes, compression generally does reduce the dynamic range, but it doesn’t have to, and sometimes it does exactly the opposite to wonderful effect.

  • Myth 5: Compression makes sounds bigger

This final myth is very personal to me.

I had the pleasure of attending an early Mix With the Masters seminar hosted by one of the acknowledged masters of mixing and, in particular, artful compression, Michael Brauer.

At one point the group was talking about compression, and someone asked Michael what he’s listening for when dialing in one of his elaborate compression schemes (if you haven’t read up on his multi-bus and five-compressors-as-one-vocal-comp techniques, you should; even if you never try them your brain will appreciate the novel approach).

This is my interpretation of what he said (and I’m OK repeating it here because I’ve since read it in interviews he’s done): pushing a sound into a compressor is like pushing an object into a stretched rubber band. The harder you push the object, the more the rubber band pushes back. Michael listens for the point where there’s a musical push-pull movement and the comp feels springy and flexible.

Not pushing enough results in too little resistance – no interesting movement. But push too far and the rubber band loses its elasticity and becomes stiff – the sound loses its life. What’s more, when you push too hard into a compressor the sound becomes small.

When he said that last bit, I remember jolting upright in my seat because I’d never previously felt like I had a masterful grasp of when to stop laying in with a compressor. I had become pretty adept at using ratio and release to control the transparency or audibility of the effect, and I was starting to feel confident in knowing what kind of attack served the sound in the mix. But where to park that threshold was still a mystery to me and had been for a long time. This nugget of insight felt like the key to solving that puzzle.

When I got back to my room in the States I immediately laid into my compressors and started listening not just for snap and swing but also for size. I became obsessed with running every track I had – every sound and bus, even my FX – through the different comps in my rack and plugin folder.

I relentlessly tweaked them in all kinds of ways – aggressively, musically, invisibly, whatever – constantly level matching and bypassing the comps to listen for one thing and one thing only: how big or small the sound became in the context of the full mix.

What I heard was a revelation. I realised I had been confounding ‘density’ with ‘size’. That seemingly small syntactic error had huge ramifications, both on my productions and on my experience of creating them. This mistake explained why I never knew when to stop digging in with a compressor.

Here’s what that mistake looked like: if I was squeezing a sound and it got thicker, I thought that was the same as making it bigger. I was enamoured with the ‘grr’, the ‘hair’ and the urgency that compression added to my sounds. When I bypassed and that density went away, I was resolute that the compressor was improving things.


The problem with making density your primary compression benchmark is that you can keep going as far as the comp will let you; if urgency is a drug, compressors are the dealers of the stuff. And they have no conscience; they’re happy to dose you up as often and as hard as you’re willing to go.

But mixing is a game of balances. Of relentless trade offs and compromises. Ultimately you don’t want every sound to be as dense as possible; instead, you want it to be as dense as necessary to transmit the emotion… and no denser.

That means attuning your ears to the proportionate spaces around each tone like the curves and twists of the pieces in a jigsaw puzzle, filling up the spectrum where necessary while preserving enough dynamics to allow the sounds, and with them the entirety of your mix, to breathe – to have air around the elements such that you feel the impact when those spaces contract and the sounds collide.

Everything in a mix must be shaped with complete awareness and respect for every other piece in the puzzle… or it won’t fit. It won’t assemble into the vivid picture that the song wants to be – a gripping story the listener wants to surrender to from start to finish.



I would like to add that guys like dBridge, Calibre, Sabre etc have all mentioned that we shouldnt use compression on breaks because of similar reasoning but related to the tempo and how most compressors dont have time to react on a busy line at 170bpm. Because (I assume) you cant really get both the attack and release to react in time accordingly, if something else is happening the very next moment.

I think compressing a single sound at the sounddesign stage, is kind of another practise altogether and that, that can be used to good effect.

fantastic. thank you! compression is one of those things that seems more like black magic than science to me…

1 BigUp

Only started to read the bit on attack but bare with me a moment.
Given that 2/3 > 1/2, doesn’t your distinction seem a little petty? Moreover, considering that nobody agrees on a ratio don’t you think you’re being a bit OTT with saying “it’s completely, utterly incorrect.”? In light of the information you’ve presented on the matter, the myth, as you’ve put it, seems relatively factual.

1 BigUp

It was taken from here;

Author is active in the comments section from what I’ve seen.

About compressing your song

This article is about compressing a song – I won’t go into compression in general or compressing individual tracks/elements of a song to keep this post on point and brief enough.

(The settings seen in the compressors above are made up – I just wanted to use a pic of Slate VBC because I like it a lot)

The reason I wanted to write about using a compressor to compress a song is that I see that there’s a lot of misinformation being thrown around on music forums (because so many people are doing it these days). Compression and mastering especially are hot topics while many music-techers are trying to learn and understand them as the tools are available to everyone – but there’s also a lot of false info out there, and as I lurk on music production forums, I see people ask for help on mastering because they want their song loud, and it’s very common to see someone say “Just compress the song a lot” or “Push it into a multi-band compressor and then maximizer” without anyone explaining why.

Well, someone not super familiar with the process does what he’s told (in hopes of getting his song loud and punchy) and often probably ends up squashing the dynamics of his song – because no-one told him why/when/how he should do it. Saying “You must compress” is a bit like a barber who says “I’ll be chopping off 5 centimeters of your hair regardless” when you ask him to trim it very slightly.

I briefly want to touch two topics: compressing a song using a “simple” compressor (often also called “a bus compressor”) as well as a multi-band one. These are from my own perspective – i.e., a mastering engineer’s perspective (mastering meaning the song is made as balanced as possible, which is a major part in mastering. If you’re interested, I wrote a post about my mastering process earlier).

I’ll leave all sorts of über-geekery out and won’t go into talking about stuff like how crossover smearing happens in the inter-aural particles of semi-transparent mastering haze…yeah, that.


What do I mean by simple? You run the whole song thru it as one signal without touching different frequency ranges or splitting it into parts in any way (see the next point, multiband, for that) [however, you may use an in-built high-pass filter, like in Slate’s VBC for example, to filter out of the signal to be compressed the low end containing a whole lot of energy so that won’t trigger the compression – we want to aim higher than that but that’s all).

So why do we use a compressor? For leveling – to make the sound balanced, more coherent, to add some “glue” (as is often said when talking about a mix where things are nicely in balance). I bet you can name a good mix where nothing sticks out and everything seems to be in perfect balance. A compressor can help you in that respect.

A compressor is best used in moderation. You don’t absolutely ram your song into it. Or, well, you can, but it’ll sound crap. I get sent songs for mastering on the regular these days, and every now and then I must ask the client to turn the master compressor off and re-send the song because it’s often been misused, and the song may sound squashed, pumping, and lifeless. Personally, I never compress by default. The compressor I use in mastering (most often Slate Digital VBC Grey) is always off, and I only turn it on if I hear it’s needed.

In mastering, by far the most common use of a compressor is to level things – it doesn’t relate to making the song loud as much as many producers seem to think in their quest for maximum loudness.

So how does it happen? What a compressor does is it reacts when the signal exceeds a set threshold, and presses the exceeding signal down, in a nutshell.

When? I use a compressor if I think the beats are too loud. The most common scenario I see is snare being too loud, and the other sounds appear too quiet compared to it – that’s not the sound of a professional song; you want a nicely “full” mix where the dynamic range isn’t too big. I’ll usually go for fast attack, fast release, play with the ratio, and set the threshold so that I get roughly 1–3 dB of gain reduction – but I HAVE to emphasize that there are no rules…you HAVE to listen. There are simply no rules in terms of all that fast/slow/numbers craze, and you could pretty much set the compressor your eyes closed as long as it sounds right.

Even Dave Pensado said something like “I don’t carve sounds – I just mess with it until it sounds right”. So you know that the “rule” that says “If it sounds right, it is right” is extra legit.

Listening is by far the most important aspect here, not seeing what happens. I listen and do whole a lot of on/off, letting my ears rest a little (especially when dealing with compression), and make sure it’s doing exactly what’s needed. It’s easy to overdo this part and ruin the song.


A multiband compressor does the same thing as the compressor described above, but it splits the signal into several frequency bands and treats them individually. For this, I use Izotope Ozone 6.

When I started looking into mastering some years ago, I, too, was told by many guys who (I thought) knew mastering to “Run your song into a multiband compressor and push all the bands into it”. No, no, no. Why? Why by default? This is where a lot of people go wrong, and that’s how
you can ruin a perfectly fine mix. You don’t necessarily need a compressor.

How I use a multiband compressor is I pretty much make sure there’s nothing happening by default, but if I hear there are sounds/frequencies that are jumping out of the mix (most often this is sub), I bring the threshold of that frequency band down in the compressor so that something starts happening: all of a sudden that frequency area isn’t as strong/offensive as it was. Maybe there’s a white noise riser sweep in the upper mids that gets too loud, or maybe the singer has been left a little too loud here and there – I first bring the threshold to the general level of the song in parts where there’s no problems so that there’s barely anything happening with gain reduction, but as the sweep (or the singing) starts to get too loud, it gets pressed down.

So, once again, we’re doing leveling here – i.e., controlling frequencies so that they don’t leap out of the mix and hit the limiter (which is the very last thing in my chain) too hard. A sound that jumps up all of a sudden may hit the limiter too hard, causing distortion. A multiband is one of the tools I use to make sure that the overall sound is balanced – I don’t use it to make the song loud per se (although it relates to that because you will need a balanced mix if you want to get a loud master, because if you have those crazy frequencies popping up and you don’t tame them, that’ll mean a loud master can be hard to achieve).


I don’t do a whole lot of compression. And when I do, I level things and keep them at bay. Gain reduction of 1–3 dB can be plenty, and more than that can often be heard (we want to be transparent / non-audible with compressing things).

You probably shouldn’t do a whole lot of it either unless you know what it does, and when you do, use it in moderation.

Approx. 70–80 % of the masters I do probably don’t see any compression at all, and I’ve heard “The master I got from you sounds so loud and balanced, and you have kept the dynamics, too” often, and it is my goal. I can admit I have also heard a bit of “The master I did / got from another mastering guy sounded way more squashed and my transients appeared lifeless”. I suppose “my sound” in music production and mastering has always been not-so-compressed.

In production, I’ve always loved saturation and running things red (in analog) to kill peaks instead of compression. Compression isn’t a major tool in getting things loud as much as many people seem to think.


You can get a similar “targeted” compression type of effect with a dynamic EQ, too, which can be more precise in some ways as it targets the set frequency range extremely accurately – being a bit like a multi-band compressor. For that, I’d recommend MAutodynamicEQ by Melda.
Long live punchy beats!