ELAN offers the possibility to merge two tiers. There are several reasons why you would want to merge tiers. For instance, one could think of a situation where two people are transcribing different parts of the same media file. If both people have finished, the transcriptions can be merged via File > Merge Transcriptions.... You can also merge tiers across multiple eaf files, using the File...Multiple File Processing... option. See Section 1.9.2.10 for more information about that.

To get the annotations of both tiers onto one tier, use Tier > Merge Tiers.... In the dialog window select the two tiers to merge and click Next. Set the criteria for merging the annotations. When checking the option Only process overlapping annotations, ELAN only merges annotations that have the same value. In this case, the values of both annotations are not concatenated, so the created annotation contains the value only once.

Enter a name for the new tier and select the desired tier type or add a new type. Next, select Concatenate the values of overlapping annotations and click Finish to create the new tier. Now all annotations of the original tiers are on the new tier. Overlapping annotations are merged to one annotation. The merged annotations begins where the first of the overlapping annotations begins and ends where the last one ends. The values of the overlapping annotations are concatenated. Optionally you can specify the value the merging annotations should have.

Merging tiers can also be used to get some time statistics of the combination of two tiers. Again, select Tier > Merge Tiers..., select the two tiers to merge and click Next. After setting the criteria, entering a name for the new tier and selecting the desired tier type, select Value in the following time format and the desired time format. Finally click Finish. Overlapping annotations are merged and the annotation's value is the total duration of the overlapping annotations. (More about annotations statistics can be found in Section 2.18.2.)

As a final example, consider an audio recognizer (see Section 2.4.3) creating not one but multiple tiers. If you want to put the annotations of those tiers on one tier, you could use the Merge Tiers... option to achieve this.