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Do loop-based, time-stretched music with Pro Tools


by Craig Anderton


Pro Tools 7.4 introduced the “Elastic Audio” feature, which allows using audio loops of various tempos within a single Pro Tools project. These loops aren’t just limited to working the constant tempos, but can also follow tempo changes.


Elastic Audio has some pretty deep features, and can do far more than just simple time-stretching. For now, we’ll keep things simple with a basic automatic warping application for Pro Tools 8 that integrates loops of varying tempos within a Pro Tools project. However, note that you can obtain even more detailed control with manual warping, using the Warp Track view.



Fig. 1: Going to the workspace is the first step in navigating to loops. (Click to enlarge.)


The first step is to find the loops you want to use. With a Pro Tools project open, go Window > Workspace (Fig. 1).



Fig. 2: Locate the first file you want to use in your project. (Click to enlarge.)


Navigate to the loop you want to use in the project (Fig. 2). This can be an AIF, WAV, Acidized WAV, or RX2 format file; it doesn’t matter, because Elastic Audio will condition the file. If needed, click on a folder’s expand button to reveal its contents.



Fig. 3: The speaker button lets you audition the selected file at its native tempo. (Click to enlarge.)


You can audition the file to confirm that you want to use it.  Click on the Preview button (the speaker button, either the one toward the top of the window, or under the “Waveform” column; see Fig. 3) to audition the loop at its native tempo. When you do this, the speaker icon turns green during playback (Fig. 4), and you’ll see the waveform drawn in the Waveform column. Note that you can click anywhere on this waveform to begin playback from that point.



Fig. 4: The “Conform to Tempo” button lets you audition the file at the project’s tempo. (Click to enlarge.)


Click the “Conform to Tempo” button (the one that looks like a metronome, next to the level meter – see Fig. 4) to hear the loop at the current project tempo.



Fig. 5: Drag and drop the file into the Track List. (Click to enlarge.)


Now drag the file into the Track List (Fig. 5). A track appears automatically in the Edit and Mix windows that contains the loop. If there are no tracks in the session, and the file is tick-based, a dialog box will appear asking if you want to import the file’s tempo. If you answer “Don’t Import,” the session will use the existing session tempo.



Fig. 6: It’s easy to specify the number of loop iterations. (Click to enlarge.)


Right-click on the loop, choose Loop, and you can specify the number of loop iterations as well as some other loop parameters (Fig. 6). Editing these isn’t necessary to conform the loop to tempo. Note that if you change the tempo (by turning off the Conductor track and entering a new tempo or using the tap tempo feature), the loop will conform to the selected tempo.


Incidentally, Elastic Audio analysis is based on finding transients. If these are ambiguous (e.g., a string pad), an Analysis view allows adding or removing transient markers to optimize the stretching process.


CraigGuitarVertical.jpgCraig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.

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