Most Audio File Editor functions are destructive, changing the files stored on your hard disk. However, you can use the Undo feature if things do not go your way.
Choose Edit > Undo (or press Command-Z).
Press Command-Period (.).
The audio file is retained in its original state, even if it appears that a portion of the editing function has occurred.
You can configure the Audio File Editor’s Undo function in the Preferences > Audio > Audio File Editor pane. For more information, see Audio File Editor preferences.