Pro Tools 10: Adjusting Vocal Timing Using Elastic Audio in Pro Tools

In the macProVideo Hub article 'Fixing Drums with Elastic Audio in Pro Tools' I introduced the topic of warping: the movement of warp markers and the underlying audio to which they are attached. The focus of this tutorial is on the different symbols that appear when dealing with Elastic Audio, their function, and their relationship to the warping techniques that Pro Tools offers.

As the article mentioned above focused on drums, in this tutorial we shall take a look at a vocal performance, to review the available tools and techniques in a different context. Where previously the task involved moving each transient to the nearest grid line to achieve a more accurate rhythmic performance, this time we shall be using Elastic Audio to adjust the timing nuances of a vocalist's performance, which will involve a more manual and selective approach.

Firstly, the assumption in this case is that the vocal has been recorded to a backing track, so finding the tempo for each section is not necessary. It is of course still necessary to 'Elasticize' the audio.

[This article is equally relevant for users of Pro Tools 9 and 10 - Ed.]

Elasticize the Audio

Elastic Audio is a real-time process, and the way that Pro Tools represents this is is by showing Elastic Audio as a series of plug-ins; for each track on which you wish to perform Elastic Audio-based actions, you need to choose which Elastic Audio plug-in is appropriate. For vocal material this would most likely be the Monophonic plug-in (other choices are Polyphonic, Rhythmic, Varispeed and X-Form—although this last choice is not a 'real-time' plug-in and renders any previous choice). Choose the appropriate elastic audio plug-in in the elastic audio pop-up selector on the track header.

Choosing the Elastic Audio Plug-in.

Hold down the Option key when you make this choice to choose the same plug-in for all tracks of the same type.

If you then click on the Elastic Audio plug-in selector you will open the plug-in window for that Elastic Audio plug-in. Note that some have variable parameters (not Monophonic, however).

Click the Elastic Audio plug-in to show the plug-in window.

Analysis View

Before looking at warping it is necessary to distinguish warp view from analysis view. Choose analysis view from the Track View selector pop-up menu and you will see the Event Transient markers created by Elastic Audio analysis. If necessary you can remove ones you don't want (Option plus the Grabber tool), move them (drag with the Grabber), or add new ones (click with Control plus the Grabber tool). For a vocal performance, one approach is to have Event Transient markers at the start of each syllable and one at the point where the last syllable of the phrase ends.

In analysis view: after analysis, before warping.

What you can't do in this view is move the underlying audio. For this you need 'warp' view. Select warp view using the Track View selector pop-up menu or use the following keyboard shortcut:

Control-Command-left or right arrow. This will change the track view to the previous/next track view on selected tracks.

Before proceeding any further I find it helpful to divide large clips up into smaller sections (vocal phrases, for example), as some types of warp can affect the whole clip as opposed to events within that clip. This can get very confusing, especially if the clip's boundaries are not visible.

Types of Warp 1: The Telescoping Warp

The most basic type of warp is the 'Telescoping Warp' which applies time compression/expansion across the whole of an audio clip on one side of a Warp marker. It is achieved by dragging an Event Marker, and there should be  no 'bounding' Warp Marker on the other side of that Event Marker. If no Warp Marker exists in the clip, one will be created as soon as the warp takes place at the relevant clip's boundary.

Telescope warp to the right, bounded by a Warp Marker at the left hand clip boundary.

Telescope warp to the left, bounded by a Warp Marker at the right hand clip boundary.

Note: to reverse the direction of the Telescoping Warp tool, hold down the Option key when dragging the Event Marker with the Grabber. Also note the Warp Indicator in the top right hand corner of the clips, which shows that warping has taken place within this clip.

To determine the section of a clip that will be affected by a Telescoping Warp, you will need to create a Warp Marker at a specific location:

1. Create a Warp Marker by Option-Clicking with the Grabber
   
2. Turn an existing Transient Event Marker into a Warp Marker by moving the Grabber tool over the Event Marker until the 'Telescoping Warp' symbol appears , then Option-click
   
3. Remove Warp Markers by double-clicking or Option-clicking with the Grabber - this will not remove the underlying Event Marker as you will be in warp view
   

Telescoping warp to the right of a bounding Warp Marker created in the middle of a clip.

Types of Warp 2: The Range Warp

Dragging an Event Marker bounded by two Warp Markers (on either side of the Event Marker) will compress the audio on one side and expand it on the other side of that Event Marker. To force a Range Warp where no Warp Markers exist, hold down the Shift key (with the Grabber tool) and drag an Event Marker. The two adjacent Event Markers (on either side) will become Warp Markers and become the boundaries of the Range Warp. This is a specific type of Range Warp called an 'Individual Warp'; this is the type that is most useful when changing the relative timing of individual syllables in a vocal phrase, without moving any of the other audio in the clip.

The Star Wars Tie Fighter symbol indicating Individual Warp.

The red area indicates over compression/expansion.

Types of Warp 3: The Accordion Warp

The final type of warp is the least useful for this specific example, but is worth knowing about. It can only be performed when there is only one Warp Marker in a clip, which should not be at a clip boundary. Dragging an Event Marker on either side of the Warp Marker causes the audio to compress/expand equally on both sides of the Warp Marker, which acts as a fixed point.

Accordion warping (note that there is only one Warp Marker).

Removing Warp 

Sometimes it is possible to make a mistake! If you want to revert the clip back to its pre-warped to state, select it and choose Clip > Remove Warp which in addition to removing any warping, proves that Elastic Audio-based editing is non-destructive!