Using Submixes in Soundtrack Pro

Posted on by Larry

[ This article was first published in the June, 2009, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe. ]

A submix is a special track inside Soundtrack Pro that collects audio from one or more other tracks for additional processing or output.

Think of a submix as a way to group tracks.

By default, there is always at least one submix in every multi-track project. Labeled Submix 1, it’s at the bottom of all the tracks in a project. Most of the time, we treat Submix 1 as the master output of our mix. But it really isn’t, and that’s what I want to talk about in this technique.


Wedged in between Busses (which is empty by default) and Master, which is hidden by default, is Submix 1. It has a header similar to a track, except that you can’t record to it.

The way that STP is normally wired, all the outputs from the tracks above Submix 1 automatically channel their audio into Submix 1. This essentially means that Submix 1 acts as the final assembly stage before output.

And, unlike the Master output, which only allows you to control final output volume, submixes can hold filters, change panning, levels, and can be set to output from one to six tracks of audio.

However, and this is a big gotcha’, Apple defaulted the output of Submix 1 to six channels (that is, surround sound), with no way to change the default. This means that if you only need one or two channels output, you MUST remember to change the output to the appropriate number of channels.

Note: I’m REALLY hoping Apple allows us to set this as a default in the next version of Soundtrack. This surround default just drives me nuts.


Just as we use folders to group layers in Photoshop or Motion, we can use submixes to group tracks. For example, if we want to fade a group of tracks at the same time, we could either do so one track at a time, which makes it really hard to make changes quickly, or group all the tracks together into a submix, then fade the submix.

Or, instead of applying effects to individual tracks, we can apply an effect to the entire group; for example, this works really well for reverb.

Or, we can use submixes to create multiple outputs of our mix; such as a dialog mix, effects mix, and music mix. These discrete mixes are sometimes called “stems.”


Here’s a six track mix I’ve assembled for this example. It has two tracks of dialog, two tracks of effects, and two tracks of music. There’s no magic to this number o ftrackss, the process is the same regardless of the tracks you use.

Let’s say we want to fade all our effects tracks to black at the same time. Here’s how.

1. Because we want some tracks grouped and filtered, while other tracks are not filtered, we need two submixes. So, go to Multitrack > Add Submix.

2. Be sure your track height is not set to the smallest setting, otherwise you won’t see the controls I’ll be writing about.

3. While not required, it is very helpful to label your tracks and submixes. In this case, I clicked the name of the track to select it, then changed Submix 1 to Effects, and Submix 2 to Everything Else.

4. Now, we need to assign each track to a submix. Because we want all our effects tracks to be grouped together, we’ll assign all our effects tracks to the Effects submix, and the other four tracks to the Everything Else submix. To do this, click the double-pointed arrow in the lower right corner of the track header and assign each track to the appropriate submix.

5. Once all the tracks are assigned, as a test play the mix and slide the Effects submix volume slider back and forth. Notice how this changes the volume of your effects without changing the volume of anything else.

6. Click the small right-pointing triangle in the upper-left corner of the track header to reveal the volume envelopes for this submix. This is exactly the same as, but a different color from, the red rubber bands that we can adjust in a Final Cut timeline.

7. Scroll to the end of your mix and add two keyframes, one where you want your fade to start and one where you want your fade to end. You add keyframes by double-clicking on the purple line. As with Final Cut, set a keyframe by dragging it.

Ta-DAH! Done.

You have now faded all your effects tracks to black at the same time. While you would not generally do this if you only had one effects track, as soon as you start creating multiple tracks, this becomes a VERY useful technique.


Next, let’s say that we want to apply a limiter filter to all the dialog tracks. I could apply the filter to each track, but, it is faster, and less computer-intensive, to group all the dialog tracks, send them to a submix, then put the filter on the submix.

1. Since we now need to separate dialog from the other tracks, let’s create another submix (type Option+Command+T) and rename this new submix Dialog.

2. Then, and this is not necessary but, I like having my submixes emulate my general layout, and I always put my dialog tracks on top. So drag the green vertical bar of the Dialog submix track header up until a faint blue bar appears above the Effect submix. It is easy to change the stacking order of submixes by simply dragging them. However, unlike video cilps, the stacking order of audio tracks has no impact on final output.

3. Here, too, we need to assign tracks to submixes. So, click the double-headed arrow on the right side of the track header and assign the two dialog tracks to the Dialog submix.

4. Select the Dialog submix by clicking the track header. (See how it turns to a light gray, indicating it is selected?)

5. From the Effects tab (in the Left Pane) select Dynamics > Limiter. You’ve now applied a Limiter filter to the submix of the dialog tracks, but none of the others.

Note: Some filters work better when you route them through a Send, which allows you to vary the amount of audio going to the submix. Reverb would be a good example of this. However, this technique is just focused on showing how submixes work, so I’m ignoring sends for the moment.

Here’s a video tutorial that shows you how to use the Limiter filter.

Here’s a video tutorial that shows you how to use submixes to add reverb.


In this example, I want to illustrate how to create separate mixes for each of your main elements – dialog, effects, and music.

You are already organized for this by creating a submix for each group. The only question now is how to output them — and that is surprisingly easy. Here’s how.

1. Once your mix is complete, save your Soundtrack Project file (Command+S).


2. Go to File > Export (or press Command+E).



3. Locate a folder to hold your audio files. There will be one file for every submix. In this case, I created a folder called “My Project Audio” and named the files “My Project Stems.”



4. Lower in this same dialog, change the output from Master Mix to All Submixes. This will output each submix to its own file. Set other key settings to output as AIFF, 16-bit, 48 kHz sample rate.


5. Click Export to output your project.



6. Open up the My Project Audio folder, inside it is a folder named My Project Stems and inside that are files for each submix.


I don’t use submixes for every project I create, only for the more complex ones. But, as you’ve seen here, submixes can provide a tremendous amount of control, which makes mixing really complex projects reasonably straight-forward and very easy.

Note: By the way, I’ve created a video tutorial illustrating the concepts in this article. You can learn more about it here.

Bookmark the permalink.

One Response to Using Submixes in Soundtrack Pro

  1. Marco says:

    and again… u saved my #ss!
    Thanx a lot!

Leave a Reply

Your email address will not be published. Required fields are marked *

Larry Recommends:

FCPX Complete

NEW & Updated!

Edit smarter with Larry’s latest training, all available in our store.

Access over 1,900 on-demand video editing courses. Become a member of our Video Training Library today!


Subscribe to Larry's FREE weekly newsletter and save 10%
on your first purchase.