November 17, 2018 – Mixing your music requires a different mindset than creating, editing, and arranging. It can and should, however, be every bit as creative an endeavor. This doesn’t mean just “winging it” and throwing on plug-ins until it sounds good. While this may work sometimes, it usually leads to painting yourself into a sonic corner that is difficult to get out of. A “top-down” approach to track organization and routing, on the other hand, leaves room to experiment and control the elements in your mix at various stages in the signal flow.
The doctrine of “top-down” mixing is based on working quickly and efficiently with minimal plug-ins, starting with the master fader, then the subgroups, and finally the individual tracks. Whether you subscribe to this approach or not, the signal flow necessary is a solid starting point for any style of mixing, and any style of music.
I like to start by cleaning up the mix window by either deleting or hiding any unused or unnecessary tracks. Next, organize your tracks so that all like instruments are placed adjacent to each other; all guitars, then all drums, then all vocals, etc.
DAWs are generally set up by default with all tracks routed to a final stereo output. This is fine during the creative stages of tracking and arranging. But mixing is all about controlling the sound of your tracks. And the more stages you have to tap into, adjust, and process the signal before it reaches the stereo bus, the more flexibility, and control you have.
Start by re-assigning the output of all your tracks to an unused Aux/Bus track. Most DAWs allow for easily re-assigning multiple track outputs by clicking in their output fields, often holding a modifier, and selecting a new destination. I like to name this new Aux/Bus track Master Bus. Having the entire signal flow arrive at a separate channel strip like this before reaching the final hardware outputs has several advantages, including the ability to process the entire mix. More on this in another article.
Routing the outputs of related tracks to a Bus or Aux before they reach the Master Bus has a lot of advantages. Subgrouping common tracks in this manner provides another stage of processing and control. For example, you might process individual vocal tracks with some EQ or compression, and then apply another band of EQ or more compression on the subgroup that will affect all of the tracks equally. You might find you have the perfect vocal blend, but they are all just a little too loud, or too soft, in the overall mix. A subgroup offers you a stage in the signal flow to control their volume all together, while still preserving all the relative balances between the individual tracks.
Sub Groups Within Subgroups
Modern arrangements often contain dozens of vocal, drum, or guitar tracks. It is often useful to route some of them into separate smaller subgroups before the signal arrives at the main instrument subgroup.
For example, it can be useful to group all verse vocal tracks together for common processing and control, separate from chorus vocal tracks which may require some different effects. The separate verse and chorus subgroups are then routed to the main vocal subgroup for control over all vocals together.
Another example where this is beneficial is with multi-tracked drums. It is useful to subgroup the overheads and toms separately for common processing before everything is routed to an overall Drum subgroup.
So far we’ve set up routing with various spots in the signal flow to tap into the audio stream for processing before the audio is summed together at the stereo output. Taking a top-down mixing approach would involve setting up some master bus processing first. Since all signals finally arrive here, you are effectively always mixing with these effects in place. Next would come subgroup processing so that when working within the individual sections, you are always mixing with these sub-group-specific effects in place. Finally, you process the individual tracks if or when necessary, when the effects already in place further downstream aren’t doing the full job.
While I do subscribe to the principles of top-down mixing, I often prefer a hybrid approach, where the first bit of processing to consider is filtering. This involves attenuating, either steeply or more gradually, areas of the frequency spectrum not directly relevant for the underlying track.
For example, if I have a guitar track featuring some funky muted picking in the higher register, the lower range of the frequency content likely does not contain any relevant information. There may be lower harmonics generated, that I want to make sure remain intact; but they only go so low.
Most multi-band EQ plug-ins contain perfectly useable high pass or low cut filters to handle the job. There are two relevant parameters to consider when applying this type of filtering. At what specific point in the frequency spectrum do you want the filtering to begin? This is usually referred to as the cut off point. And how steeply do you want to attenuate the signal below the starting frequency? The attenuation is usually measured by how many decibels the signal is reduced per octave below the filter cutoff point.
A third relevant parameter when working with filters is the ability to boost the signal right around the cutoff frequency. This is often referred to as resonance. This gives the added benefit of boosting the signal right where the fundamental tone of the audio is most important, while cutting away the less relevant information below it.
This is very useful on bass tracks for example, where you can boost right at the sweet spot while cutting away any extraneous content below. It results in a tightly focused and punchy sound.
Lo-Pass Filters work in reverse. They attenuate the content above the cutoff point, and let what is below it pass through. Lo-Pass resonance boosts in the highs on lead vocals or ride cymbals often work nicely to bring out the sweet spot up high while taming the overtones above.
With subgrouping and routing in place along with my hybrid top-down variation of applying hi and lo pass filtering where needed, the next step is to bring up the fader levels to get a rough balance between all the elements in your mix. Leave your subgroups at unity gain to start with. Bring up the faders and set the rough pan positions until things sound like they are blending the way you want. Congratulations. You have yourself the beginnings of a hybrid top- down mix.
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