When you first started mixing, chances are you treated every track individually. The snare and kick had their own EQs, compressors, FX, etc. Their output went directly to the Stereo Out, nothing fancy.
But then you started learning about using Sends, Aux channels, VCAs, etc. and your whole mixing style got a lot more complicated, very quickly! It doesn’t have to be that complicated, however, with a plan for managing advanced routing. You just need to keep it simple, and grow your style as your process matures.
But be warned, advanced routing is a potential disaster if you don’t understand how best to employ it. So in this chapter, I want to discuss the benefits of Send Effects and Sub-Groups, how you employ them without creating a mess, and why you can’t live without them.
AUX CHANNELS
There are two types of channels in your DAW that do not store recorded audio or midi regions: Aux Channels and VCAs. In Logic, they don’t even appear in your track list, just on the Console. I am not going to explore VCAs here but the difference between an Aux and a VCA is basically this: you can’t put FX on a VCA, it is merely a fader, like your Master Channel. And for the purposes of this chapter, VCAs really don’t apply.
So let’s talk about Aux Channels. There are basically two types of Aux channels: Parallel Sends and Sub-Groups.
Parallel Sends - In it’s simplest form, a Send is simply a track on your console that receives its input from another track. Adding a Send from your Kick track to Bus 21 will create an Aux track with an input from Bus 21. So now your kick track has an output to the Stereo Out and another track (Bus 21) as well.
This is also called Parallel Processing because when you send a signal from one track to another track, they will both be pushing the same sound source to the Stereo Out. But now you can modify the Parallel Channel to augment the original track.
This is commonly how we employ parallel compression or time-based effects like reverb and delay. Adding these FX to the chain of the original track might ruin it. Adding them in parallel allows us to retain the original track and manage the FX on its own.
Notice in the screenshot here the Kick is being sent to Bus 5, in parallel, which is then being compressed on an Aux track called "Punch Bus".
CAUTION: When I create a Send on a track, I always set it to 0dB or Unity Gain. I will rarely adjust the Send Gain higher or lower than 0dB. This means if you add 2dB to the fader of the original track, an additional 2dB will be sent to the send bus. As you start working with scores of tracks and Aux channels, you will be adjusting gain (faders) along the way, which will impact the gain you push to your sends and may also impact the responsiveness of the FX on the parallel channel. Unity gain allows you to manage this impact easier without additional variables like a Send that is set to +/-6dB. I don’t fiddle with send gains, I just set them all to 0dB and manage the gain/output of the send effect on its own.
Sub-Groups are different from Parallel Sends because the original tracks in the group no longer have an output to the Stereo Out. Instead, it’s output goes to an Aux channel whose output then goes to the Stereo Out. This is commonly employed when grouping tracks like all drums, vocals, guitars, etc. Since I work in Logic Pro, when I create a Sub-Group, I am typically employing a Track Stack that is not a Folder, but what Logic calls a Sum.
Summed Track Stacks should also not be confused with “Summing” which is an effect applied to all channels. Typically you will hear the term Summing when engineers are emulating the circuitry of an analog console by adding a plugin to every track. The summing effect adds harmonic distortion and color that cannot be achieved in the pure digital world. But again, Sub-Groups have nothing to do with any of this.
So when we talk about Aux channels, we need to understand whether they are either parallel to the original track (Send) or a sum of multiple tracks (Sub-Group). This distinction is critical to the foundation of advanced processing. And as we will soon see, provides an incredible amount of power to your mixing workflow.
SEND EFFECTS
When I think of Sends, the first thing that comes to mind is parallel compression. By sending your snare track to a parallel aux channel, you can compress the sustain and add more punch to the original track. This is a very common technique that is also called New York Compression, but in the end of the day it is just a Send Effect.
Once you create the new Send Effect, before you even add any effects or adjust the fader, you must understand that you have now doubled the original track signal being sent to the Stereo Out. And until you modify the new Aux you just created, it does nothing but make the original track louder.
Remember we set the Send gain to 0dB, at Unity Gain. When you double a track like this you add ~6dB to the mix. Of course once you start modifying it with compression or whatever else, the gain may increase or decrease, but you need to understand this will have an impact on the overall gain of your mix.
I will typically employ Send Effects for compression, reverb, delays, or any other FX that does not really belong in the chain of the source track. I will also employ a single reverb for multiple tracks; sending all of my vocals to a single reverb allows me to manage that reverb only once.
Here is a list of common Send Effects:
Compression - Of course compression on drums is very common, but you can use parallel compression on vocals, guitars, or anything else. Adding punch or sustain in parallel is next-level mixing!
Crush Bus - Sending all drums to a single compressor that crushes the snot out of the transients.
Room Bus - Sending all drums to a single compressor that enhances the perceived sustain is a great way to create a drum room mic.
Cymbal Sustain - Adding a send effect send to your cymbals, especially the crashes, that allows you to compress the attack and enhance the sustain allows you to add more cymbal wash into the mix.
Reverb - Sending all drums or vocals to a single reverb or multiple reverbs allows you to control the reverb without impacting the original tracks. Try not to add reverb to source tracks or duplicate reverb plugins across multiple tracks.
Delay - I don’t ever put delays on anything but Sends, even if the delay has a wet/dry dial.
Special Effects - I use the H3000 by Eventide to create a lot of vocal magic. Sending a mono track to a stereo, parallel channel, is just good mixing. This includes Flangers, Choruses, Phasers. You get the idea.
Doubling / Widening - I use the Doubler and S1 Imager by Waves quite a bit. This will take a mono track and allow me to pan it hard left and right. It is also useful for vocals on choruses where the stereo field opens-up and gets bigger and wider!
SUB-GROUPS
As we discussed, grouped channels do not perform any parallel processing. This is because the output of the original tracks are pointed to a bus, not the Stereo Out. So you are not “doubling” your source, you are just routing it to another aux channel that likely then gets sent to the Stereo Out.
Creating a Sub-Group in Logic is pretty easy, even if you are really far along in your mixing. Simply select all tracks you want to group. Here I am selecting all of my Guitar tracks:
Right-click on one of the tracks and select Create Track Stack.
You want to select Summing Stack when prompted. A Folder Stack will not create an Aux.
I employ Sub-Groups in every mix. All the drums get a Sub-Group. All the guitars, vocals, bass, synths, they all get their own Sub-Group. One huge advantage to Sub-Groups: when I need to mute or solo all vocals, including their FX, I am just one click away.
To build an effective Sub-Group, however, you need to ensure all related tracks and their associated send effects output to the same Bus. So the kick has an output to the Drum Group (Bus 1), which is where the parallel Kick Comp and Kick Verb are also outputting their signals (Bus 1). When all drum tracks and their associated Send Effects are pointing to the same Sub-Group, you can manage these tracks at a group level much more easily.
Notice in the example above all Vox tracks and Effect Sends output to Bus 10, which is the Vox Sub-Group (Aux). If you already created sends before you created the sub-group, you will need to route their output to the new Sub-Group or Summed Track Stack (e.g., Vox Verb and DDL both output to Bus 10).
Sub-Groups are especially important because they allow you to measure the aggregate peak and gain of all tracks within the group. Think of it like a pre-master channel. When I look at my drum, vocal, bass, guitar, and synth groups, it is easy to see which ones are going to give me trouble. The ones pushing too hard, clipping. You can’t just look at the individual tracks, especially if you are dealing with 30-100 of them, and expect to get the same feedback.
Summed Channels also allow you to insert FX like saturation or distortion against all tracks - including the Send Effects - in the group. So instead of applying 10-30 Decapitators to each drum track, you can apply one to all Drum tracks on the Sub-Group.
Sub-Groups also allow me to manage gain of an entire group of instruments. For example, once my vocal sub-group is balanced and mixed, I will rarely adjust the gain of an individual track. Oftentimes I find myself pushing-up or dialing-back the fader on my Vocal Group as my mixing progresses. And instead of doing this to 10-20 different tracks, I can do it on just one. This is a huge time saver especially as you are balancing the whole mix.
And finally let’s talk about Clipping and Limiting. I like to push my tracks pretty hard. Placing a Clipper like the Infected Mushroom Pusher, Free Clip, or the hundreds of other Clippers on the market to the drum Sub-Group especially, allows me to limit peaks but also push the grouped tracks even harder. Clipping a drum group can really push the loudness and bite of your drums! And it preserves the impact of the drums much better than increasing gain through Limiting which tends to soften drums rather than give them edge.
As a matter of housekeeping, I will frequently put a limiter on Sub-Groups that have a lot of dynamic. I don’t do this to increase gain, however, just cap the output. Throw down a Limiter like the L1 or the Logic Limiter, leave the gain at 0dB and set the output ceiling to whatever you are trying to stay beneath. For example I typically shoot for -6dB at my Stereo Out. This leaves room for mastering. So I like to keep my Sub-Group output around -6 to -10dB. Before I put the limiter on the sub-group, I make sure I am in the ballpark. Then I just add the limiter to the FX chain of the sub-group and set it to -6dB. If your limiter monitors for True Peak, turn that on as well.
Sub-Group Applications:
Limiting - Placing a brick wall limiter on the sub-group will tame any peaks and pre-stage the limiting you will likely apply to the Stereo Out.
Clipping - Setting a clipper on a sub-group allows you to both push more gain from the sub-group and limit the peaks. This is a useful method for many instruments, but mainly drums.
Saturation / Distortion - Adding a little saturation to a sub-group gives it more color and depth within the mix.
Glue Compression - Compressing a sub-group is what many engineers call “glue”. This is simply making all instruments in the sub-group pass through a compressor like the SSL Master G, and gives the effect of “gluing-together” all of the instruments.
Reverb - While I wouldn’t necessarily place the reverb in the sub-group FX chain itself, you may want to add a reverb send effect to the sub-group.
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