Pro Tools: Time-stretching Options Explained

The Time Shift AudioSuite plug‑in lets you experiment with playback speed. It uses an older algorithm, but the artefacts have a certain charm!

Pro Tools’ time‑stretching options enjoy both corrective and creative uses.

The ability to change the playback speed of audio has always been a powerful tool for corrective work as well as for more creative applications. To use these options confidently, it helps to understand how Pro Tools handles time internally, as different tools respond to session tempo in different ways. This article looks at the basic principles involved before exploring some practical and creative uses of time‑stretching.

Pro Tools works with two different types of time reference: absolute and relative. In Pro Tools terminology these are known as sample‑based and tick‑based time. Sample time is absolute: a second is always a second, regardless of tempo, whereas ticks (beats) are relative, meaning that the duration of a beat depends on the current tempo. You can see this reflected in the rulers at the top of the Edit window. Rulers such as Samples, Timecode and Minutes:Seconds are absolute, while the Bars|Beats ruler is tempo‑based and therefore relative. As the session tempo changes, the bars and beats move, but the absolute rulers do not.

In the Edit page you’ll see tracks display either a blue clock or a green metronome symbol, for sample‑ or tick‑based modes, respectively. This distinction becomes important when using time‑stretching or tempo‑based tools, as some operations follow tempo changes while others remain fixed. It’s worth keeping this behaviour in mind as we look at the different ways Pro Tools can change playback speed.

Offline vs Real Time

The simplest way to experiment with time‑stretching is to use a rendered, offline process. If you want to make a clip longer or shorter directly on the timeline, the Time Compression/Expansion Trim tool is the quickest option. You’ll find it by clicking and holding on the standard Trim tool and selecting the TCE variant from the pop‑up. This uses whichever time‑stretch algorithm is currently selected in Pro Tools’ preferences, and allows you to lengthen or shorten a clip simply by trimming it.

Elastic Audio, on the other hand, doesn’t render a new file; rather, it applies time‑stretching in real time at the track level, allowing clips to conform to session tempo changes. It can be enabled for an entire track, and individual clips can then be adjusted using warp markers. This makes it particularly useful while writing or arranging, when the tempo of the session may still be evolving.

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