What function does the track lock button serve in a timeline?

The track lock button in a timeline serves a critical function in digital video editing by securing a specific track so that no changes can be made to it. When the track is locked, this means that editors can prevent accidental editing, trimming, or deleting of clips on that track. This is particularly useful when working with complex projects that involve multiple audio and video layers, as it helps to maintain the integrity of certain elements of the timeline while still allowing edits on others. By locking a track, editors can focus on making changes to unlocked tracks without the fear of altering or disturbing the content in the locked track.

In contrast, the other options do not accurately describe the purpose of the track lock button. For instance, keeping a group of clips together pertains more to grouping functions rather than locking tracks. Removing a selected part of a sequence relates to editing actions that modify the timeline rather than preventing changes. Similarly, selecting every clip on a track involves selection tools, which are different from the locking mechanism provided by the track lock button. Thus, the primary clarity lies in understanding that the track lock is exclusively about safeguarding a timeline track from modifications.