The top audio track in this folder has been frozen, as indicated by the illuminated snowflake button. While frozen, it can’t be edited — but you can easily toggle its freeze status on and off.
When should you Commit your audio, and when should you Freeze it?
Nowadays, most Pro Tools users have systems that are powerful enough to handle all but the most demanding tasks in real time. We take this for granted until there is a reason why we might want to render the results of our real‑time processing. At this point, we encounter a number of overlapping features in Pro Tools, all of which seem to achieve this. What are they, how do they differ, and when would each option be the most appropriate? In this workshop, we look at Freeze and Commit.
The act of rendering processing choices long pre‑dates digital recording. In the analogue days, tracking through outboard was standard practice, because hardware outboard units could only be on one track or aux at once. To apply the same compressor to multiple sources, you would have to print the results to tape. This restriction was lifted with the introduction of plug‑ins, but in the early days of DAW recording, there were limits on how many plug‑in instances a given system could host. This is the origin of the freeze function in DAWs.
Track Freeze
Track Freeze was introduced to Pro Tools at the end of 2015 with Pro Tools 12.4. Like the other features highlighted in this article, it renders tracks in Pro Tools to audio files on disk, but the particular focus of this feature is to quickly ‘flatten’ or print effects and other track parameters, for the purpose of freeing up computer resources for use elsewhere.
When you freeze a track, plug‑ins, virtual instruments, Elastic Audio, clip gain, effects and HEAT are all rendered but mixer parameters such as volume, pan and sends aren’t. There are alternative ways of achieving the same result in Pro Tools, but the strength of Track Freeze is that it is easily reversible: you can simply unfreeze a track, make changes and re‑freeze it.
To freeze a track, simply click the snowflake button in the track header (if your track height is too small you won’t see it, but you can also access it from the right‑click contextual menu). In this menu you’ll also see a Freeze Up To This Insert option, which can be useful if you wish to freeze up to a point in the processing chain but continue to work on some of the plug‑ins. Auxiliary inputs can be frozen, which can free up resources when they are hosting effects, but Master Faders can’t be.
The power of Track Freeze is the convenience with which it can be toggled on or off. If you have frozen a track up to an insert from the contextual menu and are wondering how to un‑freeze, just use the snowflake button in the Edit window track header, or select Unfreeze from the Track menu.
So, in use, Track Freeze is as simple as it is useful. Exactly what it does behind the scenes is equally straightforward. When you freeze a track in a Pro Tools session, a folder called Rendered Files is created in your session folder. A rendered file appended ‘‑FZ’ is created. Files are all mono, so stereo tracks create files labelled L and R. A new file gets created on each re‑freeze, and old files persist in the Rendered Files folder. These freeze files don’t appear in the clips list.
The clips of frozen tracks on the timeline appear greyed out and can’t be edited without being unfrozen. Mixer operations, including automation such as volume and pan, are allowed with tracks frozen.
Commit
Commit is closely related to Freeze, and does many of the same things but with a slightly different feature set and intended use case. You could use Commit to free up system resources, but typically, freezing would be more convenient, as it can be toggled on and off. Commit’s strength lies in its flexibility.
Commit is closely related to Freeze, and does many of the same things but with a slightly different feature set.
Commit renders a version of the track’s contents, but rather than creating a hidden freeze file and locking the track for editing purposes, it creates files appended with ‘.cm’, which behave just like standard clips and files. They can be edited, they appear in the clips list and they reside in the Audio Files folder. And whereas the choices of what gets frozen is restricted to either everything or everything up to a particular insert, commit offers deeper control.
The Commit Tracks dialogue lets you decide what to render, and also what will happen to the source tracks.Commit isn’t intended to be toggled on and off like a track freeze. Using the default choices, you can get back to your starting point, but for temporary renders, freeze is the best choice. To commit a track, either right‑click and select Commit, or use Option/Alt+Shift+C. You can commit up to a particular insert in the same way as you can freeze to an insert, but the control of exactly what gets committed is far greater than it is for freeze. There isn’t an equivalent to the snowflake button for commit.
Track Commit includes options to render volume, mute and pan automation, and the option to copy sends and groups. The Commit Tracks To Insert dialogue is identical but doesn’t offer pan automation. The drop‑down menus controlling what to commit differ in that Track Commit offers the option to commit either the selected tracks in their entirety or an edit selection, while Commit To Insert only offers the option to commit the whole track.
At the risk of stating the obvious, Commit is by design intended to involve a degree of commitment, and the extent of this commitment can be determined in the bottom drop‑down menu. Unlike Freeze, which replaces the track’s contents with a freeze file render, Commit replaces the original tracks with new versions, with track names appended with ‘.cm’. What happens to the original tracks can be selected from this bottom menu. The choices are: Hide and Make Inactive, Make Inactive, Delete or Do Nothing. Make Inactive and Do Nothing don’t really strike me as useful. The default Hide and Make Inactive is well chosen, but if you are ‘all in’ on commitment then you could do the DAW equivalent of burning your bridges with the Delete option.
Here, the reverb send (in pink) has been committed. The original track contents have been replaced by a new audio file, with ‘.cm’ added to the filename.
Another place where Commit sees use in Pro Tools is the rather smart feature of being able to drag and drop MIDI from an instrument track to an audio track of the same channel width. The MIDI will be rendered to audio, and while it isn’t appended with a ‘.cm’ the mechanism by which this happens is Commit.
Anyone who has ever used AudioSuite reverbs and delays will know how clips which have time‑based effects often need to be longer than their source clips when they are rendered, in order to avoid truncating the reverb tail. Commit handles this issue elegantly. The consolidate clips option creates a continuous file as its output, but if this isn’t selected, Commit extends rendered clips out to the point where the audio level falls to ‑144dBFS. If you are using plug‑ins which simulate analogue noise, though, this could cause confusing results!
Which One To Use?
So we have at least two ways of achieving much the same result: a semi‑automatically generated render of tracks in Pro Tools sessions with some or all of their processing ‘baked in’. Why and when to choose either depends on what you are trying to achieve. Freeze is a simple and convenient way to manage system resources. The ease with which it can be toggled on/off, the fact that the resulting files are kept out of the way, and that no additional tracks are created in sessions means it is ideal for keeping finite system resources working where you need them while always keeping options open.
Commit is the ideal choice for users who wish to share their sessions with other Pro Tools users who might not have the same plug‑ins on their systems. While another user would be able to open and play a session of frozen tracks, they wouldn’t be able to edit them in the same way as a session of committed tracks. Being able to commit up to a specific insert means that, for example, a user of a channel strip plug‑in would be able to commit this first plug‑in across all tracks but share an otherwise normal session.
Another important use for Commit is archiving. By committing tracks before backing up and archiving sessions you can go a long way towards future‑proofing your backups. Committing is also useful as a way to manage one’s mixing process. Many people favour committing to a sound at the tracking stage, and using Commit allows the mix to be about mixing committed sounds rather than creating sounds at the mix stage.
To finish I’ll mention Bounce, which can be done on a per‑track basis. While Commit can be used to create stems, bouncing offers additional control over the file type, width and format of the deliverables.
Commit and freeze share common ground but each is best suited to certain tasks. Which you choose is ultimately down to the specific task at hand.
