Selecting a part of the waveform usually results in a contiguous selection, starting where you clicked the mouse up to the point where you released it.

A non-contiguous selection can be thought of as being composed of several simple selections, several regions are selected simultaneously. Here is how a non-contiguous selection can look like:

Although TwistedWave has always been able to handle non-contiguous selections, it has recently gained more visibility with the silence detector, because it uses a non-contiguous selection to mark the silences in an audio file.

Making a non-contiguous selection

When you click the waveform, the current selection is discarded, and you start making another selection. In order to make a non-contiguous, you can option-click, and the existing selection will remain, and you start adding to it.

Additionally, you can option-shift-click and drag the mouse to remove an area from the selection.

Exactly as with a simple selection, you can adjust a non-contiguous selection by clicking on its edges, or shift-clicking if you want to avoid accidentally deselecting everything by clicking just a bit too far.

What for?

What can this be used for?

The interesting point about non-contiguous selections is that all the effects that can be applied on a selection also work on non-contiguous selections, and if you want to apply an effect with the same settings on different parts of an audio file, instead of selecting a piece of audio, apply an effect, selecting another part, and applying again, you can select all the parts you want to process simultaneously, and apply the effect.

The nice part is that TwistedWave remembers the selection you applied the effect on. If you want to apply your effect with a different preset, hit undo, and the audio you were working on is automatically reselected.

Also, as indicated above, a non-contiguous selection is a very helpful tool to mark the silences automatically detected in the sound file.