Modern Approaches: Compression

Though one of the most fundamental tools in a producer’s kit, compression is often one of the most misunderstood components of audio production (in part, due to the fact that hearing the exact effect a compressor has had on a given sound source is not as readily apparent as it is when working with other common audio tools such as equalization, reverb and delay). Generally defined, compression is used as a means to control the dynamic range of a piece of audio by proportionately reducing the level of a signal when it rises above a user-defined “threshold.” While grasping even these basic mechanics can be a bit challenging for those new to the field of audio, determining how and when to implement a compressor is often an even more nuanced task.

A compressor’s simplest function is to reduce the peaks of a signal (when they exceed the threshold), while allowing for a user to in turn increase the volume of the entire soundbite (using a compressor’s output gain) without having the original audio’s peaks pierce through or potentially clip a channel. This is why compressors are often noted for their ability to “even out” or “round out” a piece of audio: by reducing the peaks in a signal, a compressor can make both the louder and softer portions of a sound source appear more uniform in terms of volume. This is also why leaning heavy on a compressor can bring the background noise of an audio signal much closer to the foreground – an extreme reduction of a soundbite’s dynamic range can bring to life some far-off dog bark or car horn hidden in a field recording or (for better or worse) bring the electric noise that was once buried in the recording of a synthesizer up to a much more audible level.

Add to all that the fact that there are many different types of compression – multi-band compression, where only signals within a certain frequency range are compressed; side-chain compression, where an outside piece of audio triggers the compressor; and limiting, a form of compression which usually makes use of a large (10:1 or 20:1) ratio in order to prevent peaks in signal from overloading an eventual output; just to name a few – and it’s easy to see why compression is one of the harder concepts within the audio production sphere to wrap one’s head around.

In order to help us cut through the fog, we have again tapped a diverse panel of working artists to share some insight into how they approach implementing compression in their own work. From those producers who use the technique only sparingly to those who see compressors as an essential compositional tool, the second edition of Modern Approaches seeks to further pull back the curtain on the subtle art of compression.

It took me a long time to develop a proper relationship with compression – it is a dangerous tool, but one that can be super helpful too. Compression can be used as a creative, tone-shaping tool, or as a simple mix utility. Sometimes I use it to change the color and tone of a sound, sometimes it’s simply there to tame a rough sound that needs to behave, or I can use it to enhance or diminish transients. When I first started, I relied on compression as a sort of “loudness button” and my mixes suffered. Now, I really see things like parallel compression, side-chaining, buss compression or transient-shaping as tools to use sparingly. I’m still on the quest for loudness (who isn’t?), but now I look for it through headroom.

I use a mix of hardware and software for my compression. A few of my synths and drum machines are hard-patched into a Universal 4-710d (which is a preamp and compressor module), that’s a brilliant tool for shaping both tone and dynamics. For more transparent compression, I’ll use the Waves Renaissance compressor. It’s quite direct for being able to get the result you’re looking for, and some people don’t realize that it is also a handy expander. My other favorite compression tool is the UAD package of LA-2A emulations. They are so simple that I can usually dial in what I need in seconds.

I try to be chill with the compressors and not use them all over the place on tracks; I want things not to be squashed-up audio-wise, and so I prefer a lighter touch. When I use a compressor, it is to allow a sound to punch through in the mix when it is otherwise not doing so. If I record a synth and it sounds amazing but it is just not cutting through the mix anywhere EQ-wise, then I put a compressor on it or give it some saturation instead. I do use side-chains or put compressors on entire drum or synth channels to give them a boost, but there is no one instrument I always put a compressor on.

It took me a while to understand compression, and I’m still learning. I think I understood it, in theory, pretty early on, but I feel like I wasn’t able to creatively use it for a few years. It’s also not necessarily the most fun effect, it’s way more fun to throw some crazy granulator or delay on something – those are immediate effects where you can easily hear what they are doing – but with compression, it’s much more subtle.

Right now, I tend to compress throughout the entire production process. For my style of music, I tend to compress a decent amount, but still, with compression, a little bit does go a long way. I’m hyper aware of dynamics, and there are points where I can tell I’ve overcompressed and I have to reel it back, but I’m not afraid of compressing strongly, or tightly, or frequently because it is part of the music, it’s part of my sound. It’s part of hip hop: the snare needs to smack you in the face, but every word in the vocals also needs to be intelligible, and you can’t make all that happen without compression.

How I use compression depends on the intention of the track. I think the more you compress, the more you can lose the energy, the texture and the real frequency of a sound, so I tend to use less and less compression because I am more and more trying to connect with the natural essence of the sounds I am using. Natural and analog sounds are by nature a bit looser, so I tend to try to maintain as much of that as I can. Compression can give you an unnatural sound, which is a sound I can love in other productions, but in my own, I tend to want to use more round and full-frequency sounds.

[When I do use compression], I use VST plug-ins – Waves or SSL models– but it’s an instinctive thing, I don’t follow any rules, my ear and my heart tell me whether or not what I am doing is sounding good. [For instance,] I use the Tempest [drum synthesizer] a lot, and it usually needs a bit of dynamic control (especially on the kicks). In that case, I use compression to give the drum hits some personality, not in an aggressive way, but more in an attempt to give them more presence.

I almost never use compression (though, I use an API 2500 when I need it). People know my music as being very rhythmic and staccato, and I like to make my music as if every part is a rhythmic part, so compression is not necessary for me normally.

I like to see the parts of my songs as having their designated spot within a 4-D box (and I say 4-D because it is parts within a cube that are moving, so this brings it up to fourth dimension but essentially you can imagine them as 3-D because the frequencies are normally fairly stationary). With compression, you generally muddy the lines between these parts ideas, and I like to keep my music highly organized and clean.

One of the first records I bought was Adonis’ “No Way Back,” and this record didn’t seem to have any compression and yet it hit so hard. I like hard-hitting, punchy music and as much as people like to think that compression makes music hit harder, I haven’t seen much evidence of this. If you get the sounds right before you compress, then you can create the punch exactly how you want it. After I get each part exactly how I want it, then and only then will I add slight compression to tie it all together, normally in the mastering stage.

I try to not mess too much with compression until the mixdown parade begins. I try to use as little compression as possible, and instead try and compositionally herd elements around each other to avoid squashing the energy, velocity and liveliness of the individual tracks. It’s only after I’ve made a go at adjusting things by hand that I go in and do a bit of buss compression to glue certain similar tracks together, like all my hats for instance, or a family of claps, snares and percussion sounds. A few times I’ve had to use aggressive compression on an unwieldy arped synth that dives and peaks out of control, but usually I find compression makes things more mellow and congealed.

I didn’t understand compression until recently, in fact, and I usually use whatever compressors are available to me in the shitty program I happen to be using that day to make my tracks. As a tool to make things less dynamic and perhaps dangerous on a club system, compression is incredible, and what it does to bass is one of the strange audio transformations that has become a secret weapon. It’s hard to explain, but compression can make bass have a different perceived volume or energy than what you see on a decibel reader. It’s like witchcraft at this point – similar to phasing, you are psyching out your own ear.

I don’t like to use compressors for sculpting individual parts of a track, but I do use them to cut down the peaks of sounds, such as hand claps and acoustic guitars that I have recorded on my own. I also use compressors on my master tracks in cases where I would just like to cut down the peak of the track a bit.

Every so often, I do use a compressor to get a more aggressive sound from something, but a compressor is not always necessary for making an extreme sound – I find it can be made just as well using cheap amplifiers, cassette tape recorders or analog mixers.

I mostly use compression on individual elements, or on groups if I have a chorus with a bunch of equal-level sounds in it. I always use compression on the kick, to give it weight. For the rest of the sounds, I use a compressor when the sound moves its volume too much or if it sounds unsteady. Overall, I prefer using a lighter touch when using a compressor.

Compression is really trial-and-error for me. I don’t use it as much as equalization, but if I do introduce a compressor into a sound, more than likely I am just trying to tighten or loosen that particular sound. Sometimes, when I want to use an extreme sound, I’ll use compression on it. If, or when, I choose to use a compressor, I am taking into account the feel of the particular sound I am using compression on, as it aligns with the rest of the track.

A broad part of my compression spectrum comes from using different [types of] tapes and doing stuff with tape machines. A lot of elements in my productions are just tape-processed, and I find that the tape does most of the work.

When I do use compressors, it’s mainly as a corrective tool, to have control over the sounds. When I want a richer or deeper sound, something more textured, I’ll use compressors to bring out some of the background noise, especially when I’m using dirtier samples. I have access to quite a lot of compressors; hardware ones as well as the UAD plug-ins which I use for their modeled compressors.

Once I realized using the envelope on a sampler is way easier than using compression for individual sounds, I’ve really only used compressors as a groove tool. Compression is especially useful in quickly modulating the volume of grouped channels in a way that is dependent on the unique sum of their mixed envelopes. A great application of this is using the release setting on a compressor to get the group’s volume to rise up into the next beat. This is how I get tracks to be loud in the “right places” instead of just always being loud.

On the last record I did, I worked with a mix engineer, and he used way more compression than I generally do, but it sounds great, so I might start doing a lot more of that, just to make it stick out. Normally, I try not to use compression too much because I like there to be some breath around the elements in my tracks. If it’s not for the effect of sound design, I usually wait to use compression to the end of the process, when I’m fine-tuning and mixing.

I’ve almost completely stopped compressing kick drums and hits like that because I like the way uncompressed 808s and things like that sound. I know it’s a rule of thumb for a lot of people just to throw compression on kicks, but I really enjoy the breath around them that can exist when you leave them uncompressed. On vocals though, I love to compress the hell out of my voice, and I usually group all the background vocals together and compress them separate from the lead vocals.

I spend a lot of time running drums through an outboard compressor (and saturator) I’ve got called the Iotine Core. This means they’re all compressed from the start, so I don’t really think about compression from that point onward until I’m trying to sort a final mix out, then it gets a bit more creative. I’ll group sounds together and squash them a bit, but thinking about it, I probably use saturation where a lot of people would use compression – I find saturation rubs the edges off transients and allows the sounds to glue together in a way that suits me better. With more melodic bits, I tend to just leave them as they are unless the dynamics are particularly unruly.

Lately, I’ve been trying to get into side-chaining things pretty hard, just to liven them up a bit. The Jai Paul album is a good example of how that can be done well, and it really inspired me. I’m still working on it, but playing around with the NI Supercharger seems to yield some interesting results in that direction. I think when done right, extreme compression can really add something, done wrong it just sounds like a strained mess.

A few years ago, we used to be a bit heavier with our compression, and really slam things and everything was squared off completely, and it would just get too tiring on the ears. Now, If we’re working on more banging kind of club tracks, we might slam the compression pretty hard, but we try to be a bit more refined with it while still keeping things punchy and full in the low-end.

With drum sounds, we compress as we go. As we build the overall drum sound, compression becomes be part of the individual sounds, and then part of the overall rack as well – there will be a certain compressor on the kick, another one on the snare, and then another type of compression on the whole drum rack. We compress our synth sounds less than we do our drums, to let them be a bit looser and freer, but in the end stage, we might group the synths and give them a bit of overall compression.

We also do use compression as an effect. Particularly with field recordings, we like to use compression like a sort of magnifying glass; really compress something to get the floor sounds and all the sounds you don’t initially hear up in the mix. There’s usually loads of really interesting stuff you can play with that way. In the sound creation stage, we use a lot of compression to find things that just aren’t initially there or obvious to the ears.

I don’t think that it is a hard fast rule that a compressor should go on everything. There is a sonic compromise to using a compressor – it’s going to change your transients, it’s going to change your low-end – and you should try to use it as little as possible. For instance, I think there is this idea that you need to put a compressor on a bass drum because that is a technique that applies to recording an acoustic bass drum. But when you have a sampler or a drum machine playing a bass drum, velocity is your dynamic control, so you don’t need to use a compressor in that way. I think people see putting a compressor on the bass drum as a rule, and I don’t see it that way.

It can also be very helpful to automate the threshold of your compressors to react to the song. It’s not a set-it-and-forget-it device, every section of a song is different and should be different, and you should automate your devices as such. Take a break in a house or techno song, for example: if you have heavy compression on a mix and a break occurs, those breaks are drastically different in volume from the main parts of the song, where there is always a constantly really loud bass drum. So, if you are heavily limiting a mix and then you get to a break and everything jumps up because the bass drum is no longer present, and then when the drums kick back in, now your claps and everything that hits on the same time as the bass drum will now be lower than they were in the break, and you’ve essentially lost the dynamics of the song. So, I automate the entire song per section. Compression has the potential to degrade your sound quality, change your transients, change your tone and I think automation should be used instead of just running your compressors on auto-pilot.

Being completely honest, I’m a bit lazy when it comes to compression and it’s definitely something I aim to utilize more going forward (I say this often). I’ll always get the percussion and hats grouped into a buss with a compressor to glue them together and bring out the transients, and I’ll always apply some to the snares and kicks, but other than that, I usually don’t bother unless I want to use it to shape the sound of, say, a bassline. I always thought of compression as something to get elements punching out of the speakers but it can be a really nice way of changing the tone of an instrument too.

I never really used compression until recently. Sometimes a track can be a cry baby that needs a little “hug,” so that’s when I apply compression, all of which I apply using GarageBand.

I sometimes use software compressors, but not until later in the mixing process, and only on individual elements that I want to cut through the mix or have more presence. I also use light limiting on almost all melodic elements in order to melt them together a bit. I don’t ever use hardware compressors or limiters until the mastering stage, where I sometimes run everything through an UREI 1176.