Mid-side processing – that is, the differential treatment of the mono ‘mid’ and left/right ‘side’ components of a stereo signal with equalisation, dynamics manipulation and other alteration – has become standard practise in modern music production. Here are some cool things you can do with it.

Fully Separate The Mid And Side For Independent Processing

Plenty of plugins let you switch their specific processing between the mid and side components, alongside regular stereo operation, but wouldn’t it be awesome if you could simply pull the two signals apart as a discrete operation, then apply any effects you like to each one? Good news: you can! All you need to to do is run the source sound through two parallel effects chains, with the mid component muted at the very start of one and the side component at the start of the other, then whatever plugins you fancy inserted into each – chorus, delay and filter and on the side; compression, distortion and reverb on the mid, for example.

Depending on your DAW, setting this up will involve either duplicating the track to create the two parallel channels required, or using the onboard parallel ‘FX rack’ systems offered by Ableton Live, Bitwig Studio and others to run a single track through two simultaneous chains. And while you can isolate the mid and side in each chain via any M/S plugin with mute or volume level controls, for a totally dedicated solution, download Voxengo’s free MSED, which makes the setup procedure appropriately utilitarian.

Make Stereo Bass A Viable Option

It’s often said that bass should generally be kept in mono to eliminate the possibility of phase cancellation and mono compatibility issues, but when you do want to push your low-end instrumentation out to the sides for creative effect – through the application of chorus, delay and other stereo processors – mid-side EQ provides the targeted frequency-shaping you need to keep such sonic horrors at bay. Since the root of the problem is the widening of low frequencies out from the centre of the image, high-pass filtering the side component, with the cutoff at anywhere from 80-200Hz or even higher, should be enough to lift the stereo content of your bass part out of the low-frequency danger zone, while maintaining the sense of width and leaving the mono meat of the sound – the mid component – well alone.

Add Peripheral Air And Sheen

Meanwhile, at the other end of the frequency spectrum, applying a high shelving EQ boost to the side component is a great way to give any frequency-rich part a sense of spacious aeration and high-end lustre without over-brightening it at the centre of the mix, where it could become distracting. For transient-heavy sources (drum overheads, percussion, guitars, keys), any wayward jumps that might occur in the levels of those shelved frequencies can be reined in by using a dynamic EQ band set to pull the shelf back down a touch whenever the threshold is exceeded.

Make Space At The Centre

Hopefully the last two suggestions have given you some idea of the power of mid-side EQ for enhancing or suppressing the side signal, and it won’t surprise you to learn that the same principle applies to the mid as well. Most pertinently, the ability to attenuate troublesome frequencies in the mid component alone allows for a more nuanced approach to dialling down the often problematic central prominence of stereo pads, guitar busses, backing vocals, reverbs, overheads, etc, than EQing the full stereo signal. Just the thing when you need to make room for the lead vocal in a busy mix.

Mid-Sidechaining

For a more subtle take on sidechain or ‘ducking’ compression, fire up a mid-side enabled compressor such as FabFilter’s Pro-C 2 on a sustained sound (strings, synth pad, etc) or reverb channel, set it to only compress the side component, then activate the sidechain input and key it off something rhythmic – the kick drum, perhaps, or a silent trigger. The result should be a gentle undulation at the stereo extremes of the compressed sound that can bring a little more groove to the mix without compromising the central focus of the part itself.

Dynamic Widening

Following on from that, mid-side compression can also be called on to animate the perceived width of any stereo signal, with the movement guided by its own dynamic profile or that of an external sidechain input. Set your mid-side compressor to process the mid, and tweak the threshold, ratio and envelope controls so that the mono component drops in volume enough with the loudest parts of the signal to make the side component become relatively dominant, thereby giving the impression of the whole thing becoming briefly wider. This can be particularly effective with processed guitar sounds, vocals, synths and percussion lines.

Mid-Side Mastering

If you know what you’re doing and the potential issues to listen out for, mid-side plugins can be a godsend at the mastering stage, opening up various ways in which to correctively and creatively manipulate the stereo image for a more polished and ear-catching end product. From reducing low frequencies in the side signal for clarity or compressing the mid for extra width, to adding grit with a whisper of distortion on the mid (hello, FabFilter Saturn 2 and Brainworx bx_saturator 2) or fractionally raising the volume of the side signal in the chorus for a subconscious excitement boost, mid-side processing is a powerful inclusion in your mastering toolbox. As we said, though, don’t even try any of this unless you’re thoroughly confident in your fundamental mastering skills and judgement, as aimlessly messing with the mid and side components of a finished mix can lead to all kinds of damage.

Do you make much use of mid-side processing in your mixing and production work, and if so, how? Let us know in the comments.