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Elastic Audio In Pro Tools – Part 1

This article was written back when 7.4 came out (introducing elastic audio), but is still equally relevant in Pro Tools 8 as these features haven’t changed much.

Introducing elastic audio:

A few weeks back we took a first look at some of the new features available in Pro Tools 7.4, the most notable being elastic audio, or the ability to stretch and squeeze audio regions automatically in the timeline. After spending some quality time with the new features, I must say that elastic audio is simply amazing and will definitely transform the way you work in Pro Tools and save you hours of time. While there are surely an endless number of uses for elastic audio, this week I want to walk you through a basic audio loop workflow inside Pro Tools 7.4.

Elastic Loops

One of the greatest features added in Pro Tools 7 was the ability to drag and drop audio content from the finder or windows explorer directly into your session, allowing you to quickly add loops and audio samples from anywhere on your hard drive. While this was nice, the usefulness of audio loops has always been limited to the source material’s tempo, unless you want to spend the time using beat detective or manually conforming the audio material to your session’s tempo. Now, by taking advantage of 7.4’s elastic audio engine, not only can we drag and drop our favorite loops directly into a session, but these loops will also re-conform themselves automatically to the session’s tempo map.

If you have ever used apple loops in logic or garage band, or worked with Abelton live, you may already be familiar with the benefits of an elastic timeline. The workflow that I am about to show you will help get you started with elastic audio in Pro Tools, as well as showcase some of the unique elastic time features inside 7.4. Remember, to complete this example you will need to have Pro Tools 7.4 installed on your system, as the techniques I am about go over will not work in previous versions.

Example: basic elastic audio workflow in 7.4

I have prepared for this example by first creating a new blank session into which I will import and time my audio loops. I have chosen a few different loops to work with in this example (a simple drum, bass, and percussion loop), but almost anything will work. As you start to experiment with elastic audio, you may want to try working with rhythmic tracks first, as their transient detection confidence is very high and they can be re-timed relatively easily.

Step 1: Setting up

Before I begin, I want to check a specific option location in the processing tab of Setup > Preferences called “enable elastic audio on new audio tracks.”

Step 2: Importing the first loop

To import my first loop (a drum loop) into my session, I can simply drag and drop the file from my finder (or window’s explorer) into the tracks list in Pro Tools. A new track will automatically be created, and since this is the first file to be imported Pro Tools will ask me if I want to import the tempo from the loop.

In this example I will go ahead and choose “import” from the dialog. Pro Tools will now adjust the tempo ruler to match the extracted tempo from the audio loop.

Step 3: Selecting tick based audio

Because audio is generally sample based (), Pro Tools defaults the track’s time base to samples. When using elastic audio in conjunction with tempo changes, I want to change the track’s time base to “ticks” () by clicking on the track’s time base selector.

Now I can change the session’s tempo and all tick-based tracks will follow the tempo ruler just like MIDI events.

Step 4: Previewing new loops

Now that I have the tempo extracted from the first loop, I want to preview some new loops at the current session tempo, before adding them into the session. To do this I will browse and import my loops from the workspace browser, located under Windows > Workspace.


To preview the loops at my current session’s tempo I will click the “audio files conform to session tempo” icon in the workspace browser.

To preview a loop in the workspace browser, simply select the file and hit space bar or click on the preview icon. Note: you can choose to preview with loop playback or activate auto-preview by checking those options in the browser menu.

To import a file from the browser I can again just drag and drop it into the tracks list. A new track is created and automatically set to ticks with elastic audio enabled. I can continue to preview loops and add them into my session all at the same tempo, regardless of the loop’s original tempo.

Notice the elastic audio icon in the top right hand corner of the region, and next to the region name in the region’s list.

Step 5: Changing the tempo

Now that I have imported a few loops and set them up to re-conform as elastic audio, I can easily change the manual tempo in the transport or even add tempo events in the tempo editor. Notice how the regions squeeze and expand to match the bar|beat grid.

Quality considerations:

Now is probably a good time to discuss some of the fidelity considerations when stretching or shrinking audio files. While the elastic audio algorithms in Pro Tools are very good, as a general rule of thumb you don’t want to stretch or shrink your audio too much (your ears will tell you how far you can go). You can help the process out a bit by selecting the appropriate plug-in algorithm from the track’s elastic audio drop down menu. Pro Tools features 5 different base algorithms to choose from: Polyphonic, Rhythmic, Monophonic, Varispeed, and X-Form (rendered only). While a complete breakdown on the differences between the algorithms is beyond the scope of this article, try experimenting. Start with the appropriate algorithm for the type of audio you are working with and then try out different presets, listening for any changes.

More elastic audio coming up:

We have only begun to scratch the surface of elastic audio in Pro Tools. Stay tuned for elastic audio: part 2 with more tips, tricks, and tutorials on this amazing new feature.

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This entry was written by Brian, posted on October 14, 2009 at 6:00 pm, filed under Articles, PT Corner and tagged , , , . Bookmark the permalink. Follow any comments here with the RSS feed for this post.

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