Change soundclip speed without changing pitch?

How do I change the speed of a clip without affecting the pitch? I’m using Ardour to record voices with video and sometimes need to stretch or shrink a clip to fit into the right part of the video, e.g. voice dubbing.

Select the timefx mouse tool/mode (shortcut: ‘t’). Click and drag on the region to change its length without changing pitch. You may want to ensure that the grid is enabled and set to the correct units.