Mackie - T2 - User's Guide

Chapter 9: Rack Filters

9.1 What are rack filters?

If you have so far been amazed at how intuitive and instantly obvious Tracktion is to use, rack filters may come as a bit of a shock. They aren’t difficult to use as such, but it may not be immediately apparent how to use them; indeed you may not even be all that clear as to what they actually do. Don’t worry, they really are easy to understand and use with a just little hands on demonstration.

You should by now be familiar with the “aux send” and “aux return” filters; if you have not already encountered these filters, it may be beneficial to go back and review the discussion on them in the User’s Guide before reading further.

Just like aux-sends, racks can take audio from a number of tracks, and just like aux-returns, racks can inject that audio into another track. In fact, at their core, the aux-send and aux-return filters are basically stripped down rack filters.

Rack filters have two defining characteristics: firstly they can span a number of tracks, and secondly they provide a modular surface upon which you can potentially create completely new effects and synthesizers.

Track spanning — learning to share

It is probably easier to show this than to describe it, so let’s do a quick experiment with racks:

Add a new filter to Track One of an empty edit, and when prompted for a filter to insert, add a Tracktion delay.
Now, right-click the delay filter and select “wrap this filter in a new rack filter.” This will create a brand new rack filter that contains the Tracktion Delay filter. We’ll see what this actually means in a few pages time.
Next, add a new filter to Track Two. When prompted for a filter to insert, open the “Rack Filters” folder in the filter list, and select the “Delay wrapper” entry (Fig. 9.1.1).
Finally, lower the main output level for Tracktion to at least –6 dB (really, this step is worth it!)

Note: The “Rack Filters” folder shows any racks that have been created for the current edit.

Load an audio file onto Track One, or send it some audio from one of your input devices. Watch the level meters for both Track One and Track Two (Fig. 9.1.2). What is happening here is that rather than the two tracks having their own copy of a filter, as would normally be the case, both tracks are actually sharing the same rack filter. Essentially this is the same thing that happens with the standard aux send and aux return filters, but racks let you take things a step or two further, as shall see throughout the remainder of this chapter.

So why the need to lower the master volume? If you look at your master level you should see why. Despite the fact that you have dropped the master volume by 6 dB, the level meter will be showing the same level as the level meters on tracks one and two. Because both tracks are receiving exactly what was fed to the rack, with no attenuation anywhere, the level has effectively been doubled!

The thing to note here is that racks allow you to move audio from one track to another, and they do this by being in two places at once.

You may want to save this edit, as we will come back to it in a few pages time.

Building blocks — a modular world

Rack filters aren’t just useful for moving audio around, they have another, wholly different, trick up their sleeve too.

What you have seen so far is the outside of a rack filter, and much like any of the other filters you have used inside Tracktion, what goes on inside them is largely unknown. One engaging aspect of real hardware is that you can, if you are so inclined, take the lid off and poke around at the stuff that makes it all work. That’s not so easy to do with software, and most likely would be in violation of the software license anyway. Rack filters can’t give you access to the low-level workings of filters, but if you do like to experiment a little, they offer a good compromise.

In short, rack filters allow you to take a group of filters and use them as building blocks to make more powerful filters. You could, for instance, layer a number of software instruments to create powerful monster synthesisers. Maybe you’ve got some ideas for processing stereo channels differently to create some interesting stereo widening effects. Or perhaps you just want to save a few of your favourite effects chains for use across projects. Either way, it’s worth taking the lid of off rack filters and looking inside.

9.2 Managing rack filters

Adding rack filters to tracksYou can add a rack filter to a track in the same way that you would add standard filters. The filter list contains a folder called “rack filters,” which in turn contains all of the rack filters in your current edit. When you are prompted for the filter to insert, select a rack from this list and it will be added to the track as normal.

There is an alternative way to add rack filters to a track though. When a rack is selected, the properties-panel contains a draggable icon (visible at the top-right corner of Fig. 9.2.2) that can be used to quickly add a rack to the filter section. This draggable behaves the same as the “new filter..” draggable icon, but just adds the current rack filter. You won’t be prompted for a filter type to add.

The rack filter editor

To display the rack filter editor, click the “racks” button at the top-right-hand corner of the edit page. Keyboard shortcut: CTRL + G (CMD + G for Mac users). The arrange area will be reduced in size slightly and a rack editor strip (Fig. 9.2.1) will be shown below it.

If you look at Figure 9.2.1 you will notice three pins on either side of the rack canvas. These pins form the inputs (on the left-hand side) and the outputs (on the right-hand side) of the rack filter. The top-most input and output pins carry MIDI data. The two pins below carry the left and right channels of audio.

There is a name tab at the top-left corner of the rack editor. Each rack contained in the current edit appears as a tab here. Clicking a tab brings the corresponding rack to the fore.

New rack: This button displays a pop-up menu from which you can create a new rack filter:

Create new empty rack: Select this option to create a standard stereo in/out rack filter.
Load a preset rack: Select this option to create a new rack filter and load the selected rack-preset into it. If no rack-presets have been saved, this option is unavailable.

Show one rack/two racks: Use this button to toggle between one large editor canvas and two smaller ones.

Clicking inside the rack filter editor will show the properties in the properties-panel (Fig. 9.2.2).

Name: Use this field to give the new rack filter a name. The name appears over the rack filter icon in the filter view, and is used as the preset name if this rack filter is saved as a preset. It is a good idea to give racks descriptive names. Opening an edit that contains a number of cryptically named racks, after a few months have passed, is a misery you can happily avoid.

New input/output channel: Use these options to add new audio input/output pins to the rack. When you select one of these options you are prompted for a name for the pin. It is a good idea to label left and right pins accordingly, as this will make managing the rack filter easier when it comes time to place it on a track. Figure 9.2.3 shows an empty rack filter with two extra output pins.

Rename input/output channel: To rename a pin, click this button and select the pin from the pop-up list. You are then be prompted for a new name.

Delete input/output channel: To delete a pin, click this button and select the pin from the pop-up list.Delete: This option deletes the rack from the edit. Use this with care, as any tracks that require this rack will be affected.

Manage rack presets: This option allows you to add or remove presets from the preset list.

Add this rack to the list of presets: This option adds the current rack to the preset list, making it visible to other projects and edits.
Delete a preset rack type: To remove a rack preset, click this, and select the preset from the pop-up list.

Tip: You can use presets as a way to make copies of a rack. Depending on the nature of a rack filter, it may not be desirable to have it be shared across a number of tracks, but you may still want more than one instance of it. The solution is to save the rack as a preset, then create new racks from that preset. Once you are done, you can delete the preset to tidy up behind yourself.

9.3 How to build rack filters

As an example of how rack filters are constructed, let’s extend Tracktion’s delay filter to a true stereo type.

To start off:

Open the rack editor. Keyboard shortcut: CTRL + G (CMD + G for Mac users).
Click the “new rack” button, and select “new empty rack” from the pop-up menu.
Enter “stereo delay” in the name field (Fig. 9.3.1).

For this rack to do anything useful, we need to add some filters to it:

In the same way that you would add filters to a track, drag the “new filter” draggable icon onto the rack editor canvas and drop it.
When prompted for a filter to add, choose the “Delay” filter.
When you drop the filter Tracktion will ask you whether you want to auto-connect the filter; click the “no” button.

If all went well your rack should contain a single filter icon as shown in Figure 9.3.2. This filter forms one channel of our stereo delay. We now need to add a second delay, which will act as the other channel, so following the same procedure as you used to add the first filter, add a second delay filter to the editor.

When building racks it is a good idea to try and place filters tidily and in logical positions, because whilst the location of the filter makes no difference to how the rack works, it does make it easier for you to see what is going on. Filters can be moved around inside the rack editor by clicking and dragging them to the desired destination. Try moving the two delay icons around until they form a vertical line roughly half way across the editor panel. This will make it easy to see how the stereo delay works.

The final thing you need to do is to make the connections that allow the filters to talk to the outside world. On the delay filter in Figure 9.3.2, you can see there are three pins on either side of the filter icon. Just like with the rack itself, the top-most pins are the MIDI input/output pins, and the two lower pins are the left and right stereo channels. Making connections between pins is easy — just click on one of the pins and drag a line to the other. If you create a connection you do not want, you can remove it by simply clicking on the line and dragging it into an empty part of the rack canvas. Figure 9.3.3 shows the stereo delay correctly connected to the rack pins. Practise dragging the connections until you can comfortably create this circuit.

Note: The only permissible way to wire pins is for right-pointing pins to be connected to left-pointing pins, and vice-versa. In addition, MIDI pins cannot be wired to audio pins. Feedback loops are not allowed.

To create a true stereo delay effect, we need to set the right and left delay periods, so:

Select the left channel delay, or top-most filter icon, and choose “1/2 beat” from the tempo menu (Fig. 9.3.4).
Now select the other delay, and set the tempo to “1/4 beat”.

At this point you have a fully working stereo delay. Try adding this rack filter to a track, and you should hear the stereo delay effect. There is a lot more you could do with this rack to make it more interesting. Try experimenting with adding other filters to the rack, or feeding the output from one of the delays into the input of the other.

9.4 Racks, tracks, inputs, and outputs

Earlier parts of this chapter have referred to the possibility of racks featuring more than two input or output channels. Let’s now look at how this works, and how you would use such a rack.

You may recall that in Tracktion all tracks are natively stereo in nature. Given this, how can a rack with more than two audio inputs receive any input on the extra inputs? To answer this question we need to look at the properties-panel for a rack filter that has been placed in a track, such as that shown in Figure 9.4.1. The four options on the left-hand side of the image are where you select which of the rack’s inputs and outputs to connect to the current track. Clicking on one of the values will display a pop-up similar to the one pictured below. The pop-up menu shows the choice of available inputs offered by the rack.

Because the track itself is a fixed stereo track, you can only connect the track to two of the rack’s inputs and outputs at any one time. However, there are no restrictions on which of the rack’s pins you connect the track to. For example, there is no reason why you couldn’t send both the left and right channels of a track to just input four on the rack.

Looking again at Figure 9.4.1, you can see that each of the track’s input and output boxes has a corresponding level control. By adjusting these levels you can control how much of the track’s audio is sent to each of the inputs, and how much of the rack’s output is returned to the track. The “link inputs” buttons control whether the channels act as stereo pairs when adjusting the levels.

Above the level controls there are two sliders: dry and wet. These function as standard wet/dry controls, setting how much dry signal is retained, and how much of the processed signal is returned. The wet control largely duplicates the functionality of the left/right output level controls, though it can sometimes be easier to use. The dry control, on the other hand, is very important for many common rack tasks.

A basic auxiliary send

To close this section, let’s just look at what is involved in using a rack filter as an auxiliary send. If you still have the simple demo edit from the first section of this chapter, open it up ready. If not, you may want to go back to section one and follow the steps for creating it.

Just like with the aux send and aux return filters, it is best to start by nominating a return track. In this example, we will call Track Two the return track, so when you have the edit ready:

Place a reverb filter after the rack filter on Track Two (Fig. 9.4.2).
In addition, to create a standard “post fade” send, you will need to move the rack filter on Track One to the right side of the volume/pan filter.

That’s the return part taken care of, but since we don’t have a special send filter, we need to adjust the track settings for the rack on track one:

Click on Track One’s rack filter and set the dry amount to 0 dB.
Set the wet amount to –INF (Fig. 9.4.3). (In other words the exact opposite of their default states).

If you play the edit now, you should hear the reverb clearly over the audio on Track One. To adjust the send level of Track One, simply lower the left and right input level values as shown above.

To create further sends, place a copy of this rack filter on the track, set the wet/dry values as shown in Figure 9.4.3, and adjust the left/right input level values to control the amount of effect that will be applied to the track.

9.5 Working with multiple output VSTis

We looked briefly at multiple-output VSTis in the User’s Guide, but let’s take a closer look at how they work with racks. In addition, we’ll look at an alternative approach to working with multiple-output VSTis.

The track spanning approach

The first method, as described in the User’s Guide, uses the track spanning nature of rack filters to effectively place the VSTi on as many tracks as is needed.

To get started:

Create a new rack filter and name it after your VSTi.
Drag the “new filter” icon onto the rack canvas and select your VSTi from the filter list.
You will be asked if you want Tracktion to auto-connect the filter. Answer “yes,” and Tracktion will take care of wiring everything up for you.

If all went according to plan, you should see something like Figure 9.5.1.

With your rack ready, you simply need to place copies of it on as many tracks as you have outputs. Keep in mind that mono outputs will need a track to themselves however.

All that is needed now is to edit the rack properties for each track, and choose the appropriate rack filter outputs in the “left/right output comes from” boxes.

Note that the rack will receive MIDI from every track that hosts it, so you can even spread the MIDI parts across tracks. This makes a lot of sense for mult-timbral VSTis, as the various channels on the VSTi appear as normal tracks (Fig. 9.5.2).

The modular approach

If you would rather keep everything in one place, then you can wrap the entire of the arrangement shown in Figure 9.5.2 in a single rack. This allows you to use only one track, but keep the flexibility offered by spreading the VSTi across a number of tracks:

Create a new rack filter, and name it after your VSTi.
Drag the “new filter” icon onto the rack canvas, and select your VSTi from the filter list.
You will be asked if you want Tracktion to auto-connect the filter.
Unlike with the spanning approach, you should answer “no” to this question.
Once you have you VSTi in place you can begin introducing and connecting the various filters needed to create a complete sub-mix inside the rack (Fig. 9.5.3).

Although it may not look like it at first, this is the entire filter section of Figure 9.5.2 contained in one single rack. One big advantage of this approach is that this rack can be saved as a preset, and recalled with just a few mouse clicks for use in other projects.