Actions will not execute without at least one selected audio file. It is possible to write an action which does not actually require any audio files. For example, an action which manipulates a query database file and dynamically loads any required files if necessary. It may be somewhat of a pain in these actions to safely ignore any files which might have been selected, especially when running an action or sub-action as grouped.
This statement effectively forces the action to operate on a single file only. This means that you can execute stepwise or grouped and not have to worry about multiple executions of an action, regardless as to how many files are selected.
When any of the following conditions are met, the statement is ignored and the action test state is set to false, otherwise it is set to true.
You can restore the set of initial files by executing a Restore Initial Set of Files statement.
Note that the Run, Repeat With and Test statements all support a Grouped-Once mode which effectively does the same as this statement for a single run of an action.
Additional information can be found in the File Availability topic.