Compressing entire music mixes effectively can present different challenges to channel processing. We look at ways in which to achieve controllable, consistent compression that works with the music.
What Is Mix Compression Trying To Achieve?
While input channel compression can control levels and provide creative envelope shaping, for many, mix compression is different. On the understanding that mix compression isn’t used for level matching songs in the context of an album or playlist, its role for many will be as a creative tool.
Engineers often talk about ‘glueing’ the mix, which can be taken as the cohesive effect of compression that happens nearer the top of the the mix’s dynamic range. Wider conventions usually apply, such as lower ratio/lower threshold versus higher ratio/higher threshold; the shape and amount used is a personal choice. Talking to others as well as looking at the curves from a built-in preset compressor can give a second opinion on suitable recipes.
Controlling The Aesthetic
Ideally, tracks should still have an appropriate level of dynamic interest intact once they hit mix buss compression. Part of the skill in applying processing is achieving the desired amount of glue without the compression fighting any fader moves back upstream. The time honoured technique of mixing into mix compression from the start negates this for many engineers.
However this alone cannot always accommodate a living, breathing piece of music. What if the desire is to have the same compression flavour throughout the whole song including that pesky quiet intro as compared to a colossal chorus and retain dynamic interest for the entire song?
Compressor Automation
One approach can be automate the compressor itself. With ratio and time constant controls providing the flavour, gain reduction can be made consistent across soft and loud sections by automating threshold and makeup gain. This can, however, be a flow-killer and assumes the engineer isn’t working on hardware gear.
Pre-Compressor Automation
A more organic approach can be bus fader rides before the compressor. Slight lifts to quiet sections and slight dips for loud ones (maybe 3dB worth of ‘manual compression’) present the comp with more consistent levels. This avoids wild fluctuations in gain reduction for much more transparent results. Fader rides can be done in hardware or software either manually or as automation.
Loudness-Aware Compression
Using a specialist compressor that combines the approach above in one place is a third option. Not only does the engineer have absolute control, but also the potential for even more transparent gain reduction. POWAIR from Sound Radix is a unique tool that describes itself as a “dual-stage loudness leveller / compressor / limiter powered by a novel, proprietary compression engine”.
As such it can be thought of as a system of fader-into-compressor-into-limiter, bringing K-weighted loudness levelling and intelligent compression to the party. Replacing the ‘finger-on-fader’, POWAIR’s LKFS auto-leveller stage is designed to smoothly ride the levels of the incoming signal to achieve an ITU-BS 1770-compliant target loudness level at POWAIR’s output.
Watch in the video as we use POWAIR to achieve a consistently glued sound to a mix that would otherwise present a conventional mix bus comp with noticeably varying levels of gain reduction. We then explore the creative possibilities offered by its Punch and Adaptive faders. Punch affords control of wavefront level independently to its shape, while Adaptive Compression maintains an average compression action for a consistent sound regardless of input level.
POWAIR’s Features In Summary:
Novel, ultra-fast gain detection and reduction compression design
K-weighted loudness auto-leveller
Punch enables precise level control of transients during the attack period independent
of attack time
Adaptive Compression enables maintaining average compression for natural
performance dynamics
Machine learning-based perceived loudness auto makeup gain compensation
Bandpass and band-reject side-chain filter
External side-chain key input
Mono, stereo and mid/side operation modes with continuously-variable compression
link control
ITU-R BS.1770.4-compliant LKFS and true-peak output level meters
Faders And Compressors In Concert
Be it for input channels, or mix duties, using an intelligent adaptive compressor provides an elegant solution that is quicker than automating a compressor. Not only that, but can anyone working without a control surface be absolutely sure they’re not mixing with their eyes?
For some, manual compression with the fader will always be the ultimate tool to get the most out of their buss comp; mix treatments are personal, and mixes from the engineer who sounds like themself comes from years of doing. That said, having real-time automated fader rides in front of the compressor will be welcomed by some.
Having used POWAIR, all I can say is try it. Any audio people who still watch ‘linear’ scheduled TV would certainly thank broadcasters for running POWAIR… Casual observations aside, this is an audio plugin that you might want to make friends with if you like the idea of calibrated level management coupled with a transparent aesthetic where needed. However you get there, consistent mix compression is there for the taking.