vertical bars after generating silence

Could someone enlighten me what those vertical bars mean and how they can be used. I record multiple mono tracks at a time, then align them End-to-End, then drag the mouse to select the tail of one track through the head of the track just below it. The tail and head is the silent areas where one usually expects to find clicks of the keyboard, the sound of breathing, etc., which I want to eliminate. After selecting the tail and head, I do Generate > Silence. The result is that now I have vertical pairs of vertical black bars on each of the tracks. I would need to click on each of these bars to have them disappear. However, I noticed that depending on how I click on those bars, I might see that the track would move, or a certain part of it would get deleted, and some other flaky behavior that I cannot find any description in the documentation. So, I suspect those vertical bars can be useful for editing, but cannot figure out how.
Thanks for your help.

The vertical bars called “split lines” demarcate different clips within the track:

A split line will be created at the left boundary of the selection if you generate silence into a selection that ends at the end of a track.

To remove all the split lines in one go, Edit > Select > All then Edit > Clip Boundaries > Join.


Thanks for the reply. I noticed when I generate silence by selecting to adjacent and aligned end-to-end tracks, I get 2 sets of these split lines in each track. Then, when I click on one of the lines and then immediately on another line, I can either tet the section between these two lines removed, or sometimes the track slides to the right. I suspect there is some functionality in this behavior, but it eludes me for now. Can you explain the behavior above?

You don’t say what version of Audacity you are using (see the pink panel at the top of the page) but black split lines (one per track) are expected when generating into a selection that borders the end of a track.

I recommend you use the latest Audacity 2.1.0 from then Audacity Manual at will match with that version. That link always has the Manual for the latest version of Audacity.

If you double-click either side of a black split line, this selects all the audio up to the next split line (or up to the start or end of the track if there are no other split lines). The selection is not removed unless you choose to remove it.

Cut Lines behave like you describe, but those lines are cyan at first and then red, not black. Cut Lines may appear black if you are zoomed out so that a Split Line obscures a Cut Line.

Cut Lines are not on by default. If you need Cut Lines on but don’t want a Cut Line to appear, delete instead of cutting.