The more we learn about music production, the more we realise just how much control we have over the way sound effects us emotionally. Sure, a great song might have to pass the old grey whistle test (an archaic reference to a long-gone British TV show), but beyond rhythm and melody there’s an entire world of sound design that makes a piece of music memorable, impactful, and effective.
A really good way to tackle any subject that seems too vast to comprehend is to break it down into manageable chunks, and a great way to do that with effects is to categorise them as time based, dynamics based, and harmonics based. Sure, it’s not perfect, but it’s a good rule of thumb. We’ve looked at time based effects in another article, now let’s look at dynamics based effects and see just how quickly we can get to grips with the fundamentals…
In music production terms, dynamics generally refer to the range of volume from silence to a piece of music’s loudest point. You know what I’m talking about; you’re watching a tense thriller with your TV’s volume up to hear the whispered dialogue in a smoky hideout, when suddenly an explosion shakes your window panes and sets every dog in the neighbourhood into a group howl. The greater the dynamic range of sound, the more wiggle room there is for things to appear louder or quieter than each other.
The compressor is the tool in a music producer’s arsenal that controls and reduces dynamic range. By squashing down the loudest peaks of a signal, we get the opportunity to raise the entirety of the signal up. Now, instead of the really loud parts of our audio making our channel ‘peak’ with the rest annoyingly quiet, we can make the channel peak with those same loud parts, but they’re no longer quite so much louder than the rest of the signal so the quieter parts are more intelligible. We’ve quite literally ‘compressed’ the difference between loud and quiet.
Compression can be thought of as a little helper that sits automatically adjusting the volume dial on a channel for you, much like you might sit with remote in hand anxiously preparing yourself for the smash cut to a car chase that comes in way too loud compared to the love scene that’s just played out on that film you’re watching. The difference is in the surgical nature of the adjustment, though. We’re talking milliseconds, and more than that there’s also a specific amount of reduction that happens to a signal. For every 10dB a sound goes over the threshold of acceptable range, the level might be reduced by 5dB. It might take 3ms to start working, 50ms for the gain reduction to fade away. The parameters we dial in to a compressor can radically change the character of the resulting sound, and what’s more, the method the compressor uses to work its magic can make a big difference too.
You’re probably well aware of the mind-boggling number of different compressors you could potentially choose from, and the way different producers and engineers have different favourites for different tasks, despite the controls on them seemingly being exactly the same. There’s even a lesser used, but still important subcategory of compressor: the upward compressor. Rather than reducing the loud portions of a signal, an upward compressor increases the level of the quieter portions. Even though the end goal is the same, the method will change the character of the resulting sound significantly.
Compression is one of those easy to learn, hard to master techniques that we can use to be completely transparent and ‘magically’ make a signal more present and loud without altering its character, or, in another setting, be aggressive and create a completely different sound.
If compressors are one side of a coin, expanders are the other. Rather than take the loudest parts of a signal and reduce their level, an expander boosts them further, increasing the dynamic range of the signal. Expanders are useful for lots of applications, from drum breaks that could do with the kick and snare standing out a little more from the hi hats to vocal performances that seem a little flat and uncharismatic.
Because expanders essentially do the opposite to compressors, but use the same method, they’ll often have very similar controls; it’s actually quite common for a compressor to have an expander mode that uses all the same controls for threshold, attack, and release and just switches the gain reduction control into a gain increase control.
A compressor has a threshold above which it begins to work. The key difference between a compressor and a limiter is that a compressor will reduce the signal above that threshold by a ratio: for every 10dB a peak rises over the threshold its level will be reduced by 3dB, or 6dB, or whatever. The result will still be above the threshold set, just not by as much. Limiters instead see this threshold as a hard limit above which no signal can rise.
Of course, the issue with this is that the peaks don’t just become reduced in power, if they’re a large amount over the threshold they’re forced to become very unnaturally flattened out. Just like a compressor, the method a limiter uses to achieve this squashing will make a huge difference to the sound, from a saturated, thick distortion to a grating, digital sound. It’s because of this that limiters are often used either for transparent, ‘safety’ peak compression that just lop off a tiny bit of excess peak on a master channel in a pretty unnoticeable way but save us the agony of going through every channel in the mix with the near impossible task of optimising the way every channel’s level combines with every other to avoid anything going ‘into the red’ on the master… or as a heavy duty, obvious effect that squashes everything into a coherent whole and actually accentuates the interplay between the levels of individual channels combining, creating texture and a type of ‘dynamic rhythm’.
An expander makes loud sounds louder to increase dynamic range. The difference between the loudest loud and silence is increased, with more room for everything else to play. A gate does something quite similar, but it doesn’t increase overall dynamic range; gates work by reducing the level of a signal when it goes below a threshold. Whilst this doesn’t make the overall dynamic range larger — the loudest sound still measures the same above silence — it does have the effect of increasing dynamic range by altering where the ‘centre’ of the signal level is. If the signal that happens between loud and silent is reduced, the loud parts appear louder.
Gates are often used to completely remove signal below a certain level. If there’s noise in the signal that’s masked by a synth when it’s playing but is annoying when it’s not, or a microphone is picking up another vocalist as they take their turn to sing, a gate is a very efficient way to get rid of the offending noise compared to editing audio files or automating volume levels. It doesn’t have to completely get rid of a signal, though, and can be used as an interesting alternative to an expander in many situations.
Sidechaining isn’t an effect, it’s a technique that is generally — although not necessarily always — used to allow the signal from one track to control the compression level on another. For instance, it’s popular to use the signal from a kick drum to reduce the level of a bass. Just as, and on a surgical level, the kick plays, the level of the bass is pulled down to allow the kick to be nice and audible without the two low frequency signals combining into muddiness and un-useful extra energy in a piece. Aside from this technical use, sidechaining is often used creatively to create rhythm, perhaps making a synth pad ‘pulse’ against a drum break.
If you want to really get to grips with effects, improve your skills as a music producer, and make better music, then take a look at Essential Music Production. It contains hours of practical explanations, advice, audio and video demonstrations, recommended software and hardware… not just about effects, but everything you need to get really confident with taking your music production to the next level whether you’re just starting or you’ve hit that intermediate wall. If you want to improve, take a look at the best way.