The question, “What’s on your mix buss?” has been all the rage for several years now. Mix engineers have been pre-mastering their work for a long time, to ensure that the mastering engineer has a clear artistic vision before manipulating the audio.
Digital audio sound quality and mixing “inside the box” (summing in the digital domain) may have caused the latest renewed interest in mix buss processors. Digital sound has often been characterized as harsh and clinical. Character pieces like a vacuum tube compressors and limiters can do a great job of warming up the sound, making it more euphonic. Insert a Manley Labs Variable Mu stereo compressor across the mix buss, and a good mix magically transforms into a juicy record.
That said, stereo mix buss processing has inherent limitations. As an example, let’s pretend that you have set the compressor’s attack and release parameters to make the song have an exciting pumping effect, in time with the music. Think EDM (electronic dance music) as an obvious point of reference. Everything sounds good… until the producer asks you to beef up the low and and add more brightness to the overall mix. All of a sudden your once warm lead vocal starts to sizzle, and the entire mix starts gasping for air every time the kick drum happens. When you are that deeply into a dense mix, adding one more straw can break the camel’s back.
The solution to this problem is actually quite simple. Instead of processing one stereo mix buss, break the mix down into several submixes consisting of components that symbiotically work together. In the video link above, I discuss the workflow of breaking the mix into three stereo buses instead of one. Buss A is for all the vocals. Buss B contains the bass and drums. Buss C includes all the harmonic instruments that are typically panned out to the sides, leaving the center of the soundstage open for maximum vocal, bass, kick and snare punch and clarity.
Each of those three busses is independently processed. They can benefit from using different attack and release settings and thresholds, as well as different EQ curves.
Perhaps the simplest example of how to deploy this technique would be a scenario in which you want the bass & drums to have an obvious rhythmic “pump” without having the compression affecting the vocals. Further, imagine you want to brighten all the harmonic instruments a lot, without adding sibilance to the vocals. No problem with submix processing!
(Video courtesy of Dangerous Music, Inc.)