Logic’s busing options offer almost unlimited flexibility.
Logic Pro’s mixer has implemented buses for pretty much as long as it has been a digital audio workstation (remember, there was a time when Logic was only a MIDI sequencer). With an architecture based on that of analogue mixers, the Logic mixer is intuitive, flexible and robust. But every once in a while I need to remind myself that not everyone has been using Logic Pro for two‑plus decades, and that many Logic users aren’t dyed‑in‑the‑wool analogue console veterans. In particular, confusion can arise if you aren’t fully aware that sends, buses and aux tracks, while related, are three distinct entities in Logic.
Most hardware mixing consoles have several ‘aux send’ knobs on each channel. Each of these sends distributes signal from that channel to additional outputs on the mixer. During recording, these might feed musicians’ headphones. At the mix, they are usually connected to effects units such as reverbs. In this case, the (fully wet) reverb signal comes back into the mixer either through a dedicated effects return or into another channel, and becomes part of the mix along with the original signal. The benefit of using sends like this is is that multiple channels can access one effects unit, but with different amounts of each signal being sent to it. And, since this is how most music was mixed for the last few decades, Logic Pro adopted the same scheme in its own mixer.
Take The Bus
What’s left out of this explanation is that the pathway from the send to the reverb is called a ‘bus’. In an analogue console, these buses are hardwired to the sends, so when you turn up ‘aux 1’ you have no choice over which bus you are using. Technically you’re ‘busing’, but the term is rarely used in this context. In the analogue world, busing usually refers to sending a number of channels to a group, to be controlled by another ‘master’ fader.
In Logic, sends are not set in stone as they would be on a traditional mixer: each track can have a different number of sends, and those sends can have different bus assignments on each track...
DAW mixers are infinitely more flexible than their analogue counterparts. So, in Logic, sends are not set in stone as they would be on a traditional mixer: each track can have a different number of sends, and those sends can have different bus assignments on each track. The sends themselves are not numbered per se; they take on the numbers/names of the buses they feed. So send 1 on your vocal track might go to a reverb, while send 1 on your guitars could be feeding a delay, and so on. You can name buses, but Logic is unusual in that bus names are global rather than being loaded and saved with each project, so this could potentially cause more headaches than it’s worth. If it helps you keep track of your sends, you could stick to a scheme such as having all of your reverbs on buses 40‑49, delays on 50‑59, modulation on 60‑69, and parallel FX on 70‑79. Then, by glancing at the bus number, you can easily determine what type of effect you’re sending to.
Aux Tracks
When you select an unused bus from the drop‑down Send menu, Logic Pro automatically creates an auxiliary track.Once you’ve selected a bus assignment for your send, Logic Pro creates an ‘auxiliary track’. An aux track is essentially a track with a few minor limitations, the main one being that it is not actually a track. It’s a channel in the mixer. In order to have it appear in the Main window, you need to right‑click on it and select Create Track (or select it and hit Ctrl+T).
Even if having the aux track in your Main window is not a priority, creating a track for each of your auxes is still worthwhile as it then gives you the ability to move the track anywhere you want, whether you’re working in the Main window or in the Mixer. After the aux track is created, you can easily locate it in a busy mixer by holding Shift and clicking on the send slot.
In Practice
Once we have our sends routed to aux tracks, what are our options? Suppose you have a lead vocal track and you want to add some reverb to it. Inserting Space Designer or another reverb plug‑in as an insert onto the track would do, but it’s actually quite limiting. By sending part of the vocal to an aux track with a reverb inserted, we gain much more flexibility. We can ride the reverb aux track’s fader to bring the reverb level up or down as needed, or we can insert a compressor with the dry lead vocal as a side‑chain feed, to duck the reverb out of the way on the busy phrases. Additionally, we can add a chorus (or any other effect) to just the reverb.
Sends aren’t only useful for reverbs and delays. Lead vocals, bass, kick and snare drums can all benefit from parallel processing, and, once again, using sends as opposed to inserting the plug‑ins on the original tracks provides more flexibility. For example, I’ll often send bass to several aux tracks: one for parallel compression, one for stereo widening, one for distortion/saturation, and one for something out‑of‑the‑box like chorus or delay. Having a dedicated fader for each of these gives me massive amounts of control while remaining incredibly intuitive.
As a word of caution, always check the phase compatibility of parallel‑processed tracks with the original dry track!
Beyond The Traditional
So now that we’re using Logic Pro’s mixer like the analogue offering (albeit with more flexibility), where can we go from here? One break from tradition that I’m seeing — in scoring templates as well as in pop mixing — is a move away from the concept of global effects for a project, and towards creating sets of effects for each instrument group.
In contemporary mixes, it’s common for instrument groups like guitars, keyboards, synths, lead vocals, background vocals, bass and so on to all have their own buses. But you can take this further by including all the aux effects for each instrument group in the same bus. The benefit of this setup is that each instrument group is completely discrete, with none of its tracks being sent to effects outside of its group. So, when you turn your drum bus up or down, the drum reverb will follow. This also makes outputting stems much cleaner, and adds an element of control that was previously impossible.
In my mixing template, I have all of the guitars, keyboards, synths and solos bused to their own Track Stacks, but have elected to send them all to the same group of effects.
Lately I’ve been taking the above approach even further. This method works best on an instrument group that typically only has one instrument in it: bass, lead vocal, guitar solo, and so on.
Rather than creating a send and bus for each aux track, I use just one. Start by creating a host of aux tracks (from the mixer menu, choose: Options / Create New Auxiliary Channel Strip, or hit Ctrl+N). Select all of these new aux tracks and set their inputs to a single unused bus. Remember that holding Shift while doing this would assign the inputs consecutively; however, in this case, we want them to all share the same bus assignment.
Now set the bus on the send of the track in question to the same bus and turn the knob to an appropriate level. As you start adding effects to the aux tracks, you can simply use their faders to balance the level as opposed to using the send knob.
Blending Effects
Another potentially powerful application of this concept is to create original effect combinations. Rather than using these aux tracks for different categories of processing (reverb, delay, compression, saturation and so on), why not build a suite of four different reverbs, four different delays, and four different modulation effects? Feel free to insert more processing to each channel and bypass or enable as desired.
Here I have a Lead Vocal track that is housed in its own discrete Track Stack. I have one send feeding a slapback delay, and then bus 49 feeds six channels of reverbs and delays. Each of these tracks has additional processing and optional time‑based effects on their own output. The next two sends feed a chorus and a parallel channel. If I decided to add another parallel channel, I would most likely duplicate the channel (provided it was converted to a track first) and change the plug‑ins. It’s much faster than adding a new send/bus.