Warping Audio

   By Sarah C   Categories: Audio SoftwareMixing Techniques

When you are satisfied that the event markers that you have left visible in Analysis view are just those that you want, and that they are all in the right places, it is time to switch to Warp view. Warp view is where you will manually ‘time warp’ the audio, or, in other words, apply time compression and expansion to correct or adjust the timing of a musical performance or to create special effects.

In Warp view, you will add warp markers to fix (‘lock’ or ‘anchor’) event markers that identify specific locations within the audio to specific locations on the timeline. When you have fixed or ‘anchored’ one or more locations within the audio to the timeline, placing warp markers on top of event markers to ‘lock’ these down, you are then free to drag other event markers along the timeline to ‘warp’, that is, time stretch, the audio in various ways.

There are many ways to add warp markers using the pencil or grabber tools. You can click anywhere in a clip with the pencil tool to add a warp marker at that location. Typically, you will click on an event marker to create a warp marker that ‘locks’ this event to its position on the timeline.

Alternatively, using the grabber tool, you can Control-click (Mac) or Start-click (Windows) at any location in the clip to add a warp marker. Also, with the grabber tool selected, if no warp markers are present in the clip, or if warp markers are only present prior to the location at which you wish to add the new warp marker, you can simply double-click an event marker to add a warp marker on top of this. And if there are no event markers in a clip, you can double-click at any location to add a warp marker. Another way to add a warp marker on top of an event marker is to single-click, using the grabber tool, on any event marker that is located before another existing warp marker in the clip. Finally, with any edit tool, you can Right-click anywhere in the clip and select ‘Add Warp Marker’ from the pop-up menu to add a warp marker at that location: and if there is an edit selection, warp markers are added both at the start and end of the selection.

To delete a warp marker using the grabber tool, just double-click on it. Or, with either the grabber or the pencil tool selected, you can Option-click (Mac) or Alt-click (Windows) on the warp marker to remove it. You can also Right-click any warp marker and select ‘Remove Warp Marker’ from the pop-up menu. To delete all the warp markers in a selection, make an edit selection that includes only the warp markers you want to delete (and none of the warp markers you want to keep). Then press Delete or Backspace on your computer keyboard or, with any edit tool, Right-click the edit selection and select ‘Remove Warp Marker’ from the pop-up menu.

TIP

You can move a warp marker to a new position any time you like with the pencil or grabber tool selected: simply Control-click (Mac) or Start-click (Windows) and drag the warp marker to any new location.

Warp markers appear as thick black vertical lines with a triangle at the base of each to help you to distinguish these markers. Event markers are visible in Warp view, but as grey, vertical lines that do not fully extend to the top and bottom of the track (see Figure 4.17). Note that you can’t add, relocate, or delete event markers in Warp view—you have to go back to Analysis view to make these edits. However, with the grabber tool selected, you can drag event markers in Warp view—in fact, this is exactly what you are supposed to do to warp the audio, as we shall see shortly.

4.17

Figure 4.17 Warp view showing event markers in grey with a single warp marker inserted at the beginning of the clip

When a clip has been warped, it displays a warp indicator in the pper righthand corner to make it clear that Elastic Audio processing has been applied to the clip (see Figure 4.18). This warp indicator is visible in any track view, but it will only be shown when a clip on an Elastic Audio–enabled track has actually been warped either manually or automatically by tempo change, quantization, or pitch shifting. Un-warped clips on Elastic Audio–enabled tracks do not display the warp indicator.

4.18

Figure 4.18 Warp indicator visible in the top right-hand corner of the warped clip

If you are unhappy with the results of your attempts at warping your audio, you can use the ‘Remove Warp’ command in the Clip menu to undo the warping effect from any uncommitted clip whenever you like. The warp markers are not deleted, so you can have another go at the warping using your existing warp markers— or remove these and start again.

NOTE

‘Remove Warp’ can only be applied to clips and cannot be applied to clip groups. To un-warp clip groups you must first un-group the clip, apply ‘Remove Warp’ to the under lying clips, and then regroup those clips.

Manual Warping

Elastic Audio offers three different techniques for manually warping audio on sample- or tick-based tracks: Telescoping Warp, Accordion Warp, and Range Warp.

Telescoping Warp lets you warp the audio in the clip that occurs before the first warp marker that you have inserted or after the last warp marker that you have inserted. The important thing here is that no other warp marker should be constraining the section of the audio clip that you would like to warp.

Typically, you will apply Telescoping Warp after you have anchored the start of the clip to the timeline using a warp marker. Then, when you drag any later-occurring event marker in the clip to the left or right, all of the clip will be compressed or expanded in time from that fixed clip start point.

On the other hand, you could place a warp marker at the end of the clip. To warp audio before this marker, you would have to Option-click (Mac) or Altclick (Windows) instead.

Accordion Warp lets you expand or compress the audio equally on both sides of a single warp marker in a clip. This is particularly useful when the most important event of interest, such as the first beat of a bar, occurs in the middle of the clip.

To use Accordion Warp, just add a single warp marker at the point in the clip that you want to remain fixed on the timeline and use the grabber tool to drag any event marker that occurs before or after the single warp marker to the left or the right. The audio will compress or expand, rather like the bellows of an accordion.

With Range Warp, the idea is that you fix two points within the clip to the timeline using warp markers, then warp the audio that lies in the range between these using the grabber tool to drag any event marker that is included within this range. As soon as you move the event marker to the left or the right, a warp marker is added on top of the event marker and the audio is compressed or expanded on either side of this marker. The audio that lies outside the two bounding markers is not affected. Range Warp is particularly useful when you need to make corrections or adjustments to sections within a selected clip without disturbing the audio elsewhere in the clip.

Matching Beats Using Telescoping Warp

One of the most useful applications of Telescoping Warp is to match the beats within a piece of music to the session tempo and Bar|Beat grid. Let’s go through an example here. First you would set the Main Timebase ruler to Bars|Beats, enable Grid mode, and set the meter and initial tempo appropriately. Then you enable Elastic Audio on the track, select Warp view, and use the pencil tool to add a warp marker at the first beat of the first bar within the clip—see Figure 4.19.

4.19

Figure 4.19 Adding a warp marker using the pencil tool

If the clip does not already start at the location on the timeline that it should start at, use the grabber tool to drag this first warp marker to the exact Bar|Beat location where you want the downbeat of the audio file to start—at the beginning of Bar 106 in the example shown in Figure 4.20. It is best to use Grid mode for this so that the clip will snap exactly to the bar.

4.20

Figure 4.20 Dragging the clip by the fi rst warp marker using the grabber tool

Once you have the first warp marker in place and positioned correctly on the timeline, click on the event marker on the first beat of the second bar of the clip (with the grabber tool selected). The cursor will change to a left-right arrow to indicate that you can move the marker to left or right to warp the audio—see Figure 4.21.

4.21

Figure 4.21 Using the Telescope Warp feature

The warp marker at the beginning of the clip locks this to the timeline at this location (bar 106 in this example) so that when you warp the audio to reposition the start of the second bar (bar 107 in this example), the position of the start of the first bar does not move.

When you drag an event marker to line up with a bar line in the timeline (see Figure 4.22), this will warp the audio (a bit like stretching out or folding back a telescope with the eye piece fixed in front of your eye) until the event marker matches the corresponding bar number in the Bars|Beats ruler. This is why this is called ‘telescope’ warping.

4.22

Figure 4.22 Notice that the event marker has been moved to line up with the beginning of the second bar of music, bar 107

TIP

If you use grid mode, all you need to do is to move an event marker toward a bar line and it will snap the marker to the bar line precisely.

If there are no tempo variations within the audio, all the first beats of each bar should now line up with the bar lines in Pro Tools. If there are tempo variations within the audio file or clip that you are working with, you will have to add a warp marker to the first beat of the next bar and repeat this process for each bar where the tempo changes.

In my example clip, there were slight tempo variations throughout the audio, so I added a warp marker at the beginning of the second bar of the audio clip to lock this to its correct location on the timeline—see Figure 4.23.

4.23

Figure 4.23 Add a warp marker to lock the beginning of the second bar to its correct location on the timeline

Then I examined the event marker at the start of the third bar of the audio— see Figure 4.24.

4.24

Figure 4.24 The event marker in the third bar of the audio does not line up with the correct bar (bar 108 in this example) on the Pro Tools timeline

This did not line up exactly with the correct bar in the timeline either, so I moved this to the correct position—see Figure 4.25.

4.25

Figure 4.25 The third event marker is lined up with the correct bar line in the timeline as shown in the Bars|Beats ruler

By this time I was beginning to understand how all this works, but realized that I was losing time by switching from the grabber tool to the pencil tool. So after I had moved the third event marker into position, I looked for a shortcut. As the manual explains, instead of changing to the pencil tool to add the warp marker, you can just Control-click (Mac) or Start-click (Windows) on the event marker using the grabber tool—which saves you the trouble of switching tools. See Figure 4.26.

4.26

Figure 4.26 Control-clicking on an event marker to add a warp marker

I went through the whole eight-bar clip, carefully positioning each event marker at the beginning of each bar to correspond with the correct bar line in the timeline, adding a warp marker at the start of each bar each time to lock down these positions so that the preceding audio would not be affected when I warped audio that followed. See the eight completed bars in Figure 4.27.

4.27

Figure 4.27 Eight bars of drums, with each bar warped to exactly match the bar lines in the timeline

NOTE

A small icon, the warp indicator, is added to the clip in the top right-hand corner of each channel to indicate that this clip has been warped—that is, that Elastic Audio processing has been applied to the clip.

TIP

If you are working with a recording of a whole song or piece of music lasting three minutes or more, it can be very helpful to set up markers for all the sections first and to use Tap Tempo or trial and error methods to establish the approximate tempo of the audio. You may also fi nd it helpful to trim the audio so that it starts on a downbeat and finishes immediately before a downbeat so that you have an exact number of bars (you can deal with any stuff at the start or the end separately after you have sorted out everything else). Remember that you can always select the clip, open Beat Detective, and tap along with the music to let Beat Detective work out the length of the selection for you. But, ultimately, you should carefully count the bars while listening to the audio playback to make sure that you know exactly how many bars you actually have and to make sure that your section markers are more or less in the right places. Then, when you examine event markers in Analysis view, you can see if these are placed in sensible positions within the audio clip. Even though the bars and beats in the audio may not yet correspond totally accurately with the bars and beats in the Timeline, they should be somewhere nearby. So, with a bit of luck, you won’t get too confused!

You can also ‘telescope’ audio that occurs before the first warp marker in the clip. You might want to do this if you are working on a sound effect that preceded a visual event such as a creak before a door slam, for example. In this case, you would insert a warp marker to lock the position within the audio clip containing the sound of the door slam to the position on the timeline where this occurred, then telescope warp the sound of the creak that preceded this to get it to sound right. To telescope warp audio that is before the first warp marker, select the grabber tool, then Option-click (Mac) or Alt-click (Windows) and drag any event marker that is before the first warp marker in the clip to the left or right.

Accordion Warp

The way Accordion Warp works is that you lock down a particular position in the audio clip that you are warping, such as the central point, then drag the leftmost or rightmost event marker toward or away from this position to compress or expand the audio like an accordion’s bellows.

To try out Accordion Warp, I took one bar of music in 6/4 time signature containing six quarter note drum hits and adjusted the position of this on the timeline in Analysis view so that the fourth beat lay exactly on a quarter note grid line. See Figure 4.28.

4.28

Figure 4.28 One bar of drums played in 6/4 meter, correctly lined up on the timeline in Analysis view

Then I switched from Analysis view to Warp view and added a single warp marker on top of the event marker at the fourth beat, right in the middle of the clip, using the grabber tool: ensuring that this beat would stay locked to the timeline. See Figure 4.29.

4.29

Figure 4.29 A warp marker is added in Warp view to lock down the fourth beat, in the middle of the clip

With the grabber tool still selected in Warp view, and using Grid mode with the grid set to quarter note resolution, I dragged the leftmost event marker in the clip to the right—see Figure 4.30. This was a bit like squeezing the bellows of an accordion: the audio either side of the warp marker was brought in toward the warp marker that was fixed in position on the timeline—allowing me to hear the effect of the six beats playing in the time of four.

4.30

Figure 4.30 Dragging the leftmost event marker to the right using the Accordion Warp method causes both the start and end points of the clip to move equal distances toward the middle

When I dragged the event marker to the right again, this snapped to the next quarter note grid line—allowing me to hear the effect of these six beats playing in the time of two. See Figure 4.31.

4.31

Figure 4.31 Dragging the leftmost event marker more to the right compresses the audio on the timeline so that the six original beats now play in the time of two of the original beats.

This Accordion Warp technique works fine in Slip mode as well, which would be the more appropriate mode to use in many circumstances where you want to continuously adjust the duration of the clip until it sounds the way you like it.

Range Warp

So far we have been moving event markers, warping the audio to the right or left of these, then locking these event markers into place by inserting warp markers on top of them. Elastic Audio also lets you warp the audio between two fixed points within a clip using its Range Warp feature.

Excerpt from In the Box Music Production: Advanced Tools and Techniques for Pro Tools by Mike Collins © 2014 Taylor & Francis Group. All Rights Reserved.

RELATED POSTS:

No Comments

Tell us what you think!

*

The Latest From Routledge