Master bus compression - quite simply, the use of a compressor on the master or mix bus - can make a profound difference to the overall sonic quality of a mix, binding its individual components together into a cohesive, professional-sounding whole.
With great power, though, comes great responsibility, and if you don't fully understand what you're doing with the controls of your compressor, you can do considerably more harm than good. With that in mind, here's a quick guide to get you started.
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Step 1: Master bus compression is an often-misunderstood technique, so let's look at how to use it effectively. Create a new audio track in your DAW and drop CM205 Track.wav onto the channel. We load Native Instruments' Solid Bus Comp - a plugin emulation of the classic SSL G-Series Buss Compressor - as an insert on our track.
Step 2: We set a low Ratio of 1.5:1, 0.8s Release and a Threshold of 6.0dB, before re-levelling with a 1.5dB Make-up gain amount. A very slow Attack setting will ensure we preserve transients, so the compressor only gently pulls down the track's sustain elements - try out fast attack times and note the destructive effect of the compression. We settle upon the slowest 30ms Attack time.
Step 3: Extreme compression effects are generally best used at the mix stage, when you have more control over individual tracks and groups. Our smooth 1-2dB gain reduction is extremely subtle, but serves to gently 'gel' the overall mix together. You might not notice this 'gluing' effect unless you listen on good quality headphones or monitors - bypass the plugin to carefully observe its effect.