Label Tracks

From Audacity Manual

Creating Labels

Suppose that you have a recording and you want to annotate the questions and answers so you can easily jump directly to a particular question or answer later on. Initially, you may have something like the image below. Without any annotation it's almost impossible to tell them apart just looking at the waveform.

Here, we select the first question with the mouse (below). This may require listening to the audio several times to determine the exact boundaries of the selection.

Now choose Add Label at Selection from the Tracks menu, or type its keyboard shortcut ( CTRL+B on Windows/Linux or CMD+B on the Mac). This creates a new label track and a blank label outlining the current selection (below).

The cursor is automatically positioned inside the label, so just type the name of the label and then press Enter. Pressing Enter then allows you to use any current keyboard shortcuts normally, so you could press spacebar to listen to the selection again if you wished. In the image below we've typed Question 1.

After this question comes the answer from the person being interviewed. We'll select this one by starting from the right side of the answer and dragging to the left. Note that a vertical yellow guide appears when we get to the edge of the first label, making it easy to line up the two labels (below). It's common for the next label to start exactly where the previous one ends, but it's not necessary.

Once again, choose Add Label at Selection to create the next label, then type its name and press Enter. Then in the following image, we've added even more labels.

And here is a complete label track with several labels

Selecting a label

Whenever you click on the title of a label inside the label track, it selects the label and also selects that range of audio in all audio tracks. It also lets you edit the name of the label.

Press TAB to move from one label to the next, and SHIFT+TAB to move backwards.

Deleting labels

There are two ways to delete labels:

• Click on the label's title to select it, then press the Backspace key on your keyboard until the title is gone. Once the title is empty, press Enter or just press Backspace again to delete the label. Currently, it's also possible to delete a label by selecting a region over the label (be careful not to drag the selection up into the audio track as well), then Edit > Silence Audio. Both these methods will let any labels further to right retain their current position.

• You can also select a region extending over a number of labels then use Edit > Cut (which copies the label to the clipboard) or Edit > Delete. Note however that this method currently causes any labels to right to move backwards by the amount of the deleted selection region.

Another way to delete labels is to just remove the label track entirely and start again. Click in the track and then choose Remove Tracks from the Tracks menu, or alternatively click in the close box in the upper-left corner of that track.

Like everything in Audacity, any edits to label tracks can be undone.

Editing labels

You can change the time boundaries of a label by clicking and dragging the little handles on either side of each label. There are actually two handles on the side of each label, or three where two labels meet. The purpose of these is so that you can either adjust just one label, or two neighboring labels together.

At the junction where two labels meet, click and drag the center circle if you want to adjust both circles simultaneously. If you want to adjust just one label, click on the triangle corresponding to that label and the neighbor will be unaffected. This is illustrated in the image below. On the left we move two neighboring labels together by clicking on the center circle and dragging. On the right we move just the label on the right by clicking on the triangle on the right and dragging:

There is also a handy feature whereby you can select an area of text in a label, then right-click (control-click on a Mac) and cut or copy that text. This allows you to click in another label, right-click or control-click, then paste that text in. So in our example you could select and copy "Question" and then paste it into the appropriate labels without having to type that word every time.

Sometimes it's useful to edit multiple labels at once using a tabular view, similar to editing a spreadsheet. To do this, select Edit Labels from the Tracks menu, which brings up a dialog box showing all of your labels:

Use the arrow keys to move between cells. Handy buttons in the dialog let you insert or delete labels, or import and export labels to a file (see the section on importing and exporting below).

Linking labels with audio tracks

By default, label tracks in Audacity Beta are now linked  to the audio tracks above them, and form a track group. A track group is defined as a set of one or more audio tracks above each other, followed by a set of one or more label tracks. This is a significant change in behavior from previous Audacity versions.

Linking means that labels now remain attached to their original point or region in the audio, even when changes are made to the track length (such as by cutting, pasting or changing the speed). Thus, an action performed in any label or audio track in the group has a corresponding effect in the other tracks in the group. For example, if a group consists of one audio track above one label track, deleting part of the audio track deletes that part of the label track, and deleting part of the label track deletes that part of the audio track.

In the following example, there are two track groups. The first group comprises Audio Tracks 1 and 2 followed by Label Tracks 1 and 2, and the second group comprises Audio Track 3 followed by Label Track 3:

Note in the image above, the highlighted selection region in the first track (from zero to six seconds on the Timeline) which extends either side of Label 1. That region is highlighted in only the first track because only the first track is selected, as shown by the different colour in the Track Panel. If we now Edit > Delete the region, we end up with the following image, and get the same result no matter which of the first four tracks we select:

Note that because the audio and label tracks are linked, Label 1a is deleted, and Labels 1b and 2 both move backwards six seconds. Thus Label 1b remains attached to the quieter audio it relates to, while label 2 still remains remains two seconds in front of label 1b.

The following Audacity features also work with track groups:

• Inserting audio, whether through pasting or using the Generate effects, shifts all the grouped tracks correspondingly.
• Dragging any track in a track group with Time Shift Tool will also move the label, and any other tracks in the group.
• When using Effect > Change Speed and Change Tempo, tracks remain synchronized. Slowing down a track inserts silence into the other linked tracks. Speeding up a track inserts silence into that track, to achieve the same result.

• Click the button with the chain link icon (see right) on the Edit Toolbar
• Click "Link Audio and Label Tracks" in the Tracks Menu.

To re-enable linking, click the button or menu item again. To disable linking of a particular audio track, click on its Track Panel, drag it downwards then drop it underneath the last label track in the project.

Adding labels while playing or recording

One of the easiest ways to create labels is while you're playing or recording. There's a separate command for this, Add Label at Playback Position, also in the Tracks menu, or you can press its keyboard shortcut, Ctrl+M. Note that despite the name of the command, it doesn't only work while playing an existing track; you can use it while recording a new one, too.

Note the difference between this and the previous command, Add Label at Selection. While playing or recording, both commands are useful. Use Add Label at Playback Position to mark the exact spot you're listening to, or use Add Label at Selection if you want to make selections to label with the mouse while you're simultaneously listening.

Importing and Exporting labels

Labels are saved whenever you create an Audacity project. Sometimes it may be useful to use these labels in another program, for example if somebody wanted to know the time where each piece of an interview starts or stops. Audacity exports labels in a very simple tab-delimited plain text format that looks like this:

0.285874 -> 6.098646 -> Question 1
6.098646 -> 13.054914 -> Answer 1
13.054914 -> 20.916450 -> Question 2
20.916450 -> 28.777986 -> Answer 2

The first column has the start time in seconds, the second column has the end time, and the third column has the name of the label. Start time and end time are identical if the label marks the cursor position rather than a selection region. Values are separated by tab characters (shown as -> in the above). The exported file is called "labels.txt" by default. It can be opened by any text editor, or by a spreadsheet program.

You can export labels using the Edit Labels dialog box, or by selecting Export Labels... from the File menu. Labels can be imported using the Edit Labels dialog box, or by selecting Import > Labels... from the File menu.