Back to basics this week with a look at buses. These are a very common source of confusion for novice users. Exactly what buses are and how you might use them is so important that even if you think you’re getting by without them, you’re already using them in your sessions even if you don’t know it yet.

What Is A Bus?

A bus is an internal connection within Pro Tools and it can be used to send combinations (or “mixes”) of signals from place to place within the mixer. If you have never come across the word before it’s worth noting that this isn’t Pro Tools terminology and buses are used for all sorts of data, not just audio. Routing channels of different ‘widths’ (mono, stereo.5.1 etc) is simpler than it used to be since the introduction of automatic downmix and fanout of channel widths in Pro Tools 2021.8. Instead of having to manage these changes of channel width yourself Pro Tools now does nearly everything automatically - Any channel can be routed to any bus and any bus to any channel. Even if you think you have never used a bus in a session you will have, as the main output of your session is a bus. More on this later. If you find the idea of buses difficult then the best way to understand them is to use them. Here are five ways you can use buses in your sessions:

1. Submixes

By assigning tracks which “belong together in some way” (I’m deliberately avoiding using the word group here…) to a bus instead of the main output it is possible to bring these tracks together for processing on a shared Aux Input (or Routing Folder Track). This can be done for convenience, as more sources can be processed through fewer plug-ins or because it sounds different. The most obvious example of this is the difference between compressing source tracks individually or submixing the source tracks and compressing the submix through a single compressor. While in both scenarios all the source tracks get compressed, the results from these two approaches sound significantly different.

Many new users assume that the reason for creating submixes by bussing either through Auxiliary Inputs or Routing folders is for level control but mix groups and VCAs exist for this purpose. While you can use subgroups for level control the real point of them is to bring audio together for processing. Another really significant use for submixing via buses is for printing stems. It has always been possible to route via a bus to an audio track instead of an aux input. In the bounce to disk dialogue alternative sources other than the main output can be selected and the output of a bus can be bounced in exactly the same way as the main output. Alternatively you can use the Track Bounce command on the Auxiliary Input or Routing Folder to which a submix is routed to achieve the same result.

2. Effects Sends

Another very common use of buses is in setting up send-return loops for sharing effects across sessions. By using sends to route the desired signals to the input of a plug-in inserted on an auxiliary input, that effect can be shared across as many tracks as you like in your session.

3. Keying

A third use for buses is for routing signals as external key inputs to side chains in dynamics processors. By using a signal to control an aspect of another signal things can get very interesting. While Pro Tools uses a traditional approach to side chains and key inputs which mirrors the way these things were done on analogue equipment we are seeing more and more software which allows audio tracks to modulate almost any parameter rather than just dynamic processors.

4. Multiple Buses Using Ctrl

The fact that a track can be routed to more than one bus at a time becomes apparent fairly quickly when you start to use auxiliary sends. If you want a signal to go to multiple buses at the same time then sending to one bus from the main track output selector and a different bus from a send is fairly straightforward. If you want the level going to both buses to follow the main fader then create a post fader send (the default) and if you want them to be independent of each other create a pre fade send using the blue “Pre” button on the send. Something many people don’t realise is that it is possible to assign the main track output to multiple buses by holding Control (Start on windows) and assigning to another bus or output. A “+” will appear in front of the output to indicate that multiple outputs have been assigned. Use this anywhere you would use a post fade send left at unity to duplicate an output. Since Pro Tools 2018.7 it has been possible to select multiple buses (or inputs/outputs in a single operation). This still uses Ctrl (Start on a PC) but multiple destinations can be now be selected without having to reopen the menu each time, which wasn’t the case previously. Ticks next to each selected bus indicate the current routing.

5. Mapped Output Buses

Outputs in Pro Tools are no longer simply connections to physical outputs in your system. Since Pro Tools 9 they have been buses which are “mapped” to these physical outputs and it is this intermediary bus which builds in the flexibility into the system to allow easier transfer of projects between systems with different outputs.

Free Video Tutorial

in this free video tutorial brought to you with the support of Avid we look at the most common uses of buses in Pro Tools.

Getting further into Buses, in this premium tutorial Julian examines some less discussed aspects of bussing.

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