Processing : AudioSuite Processing : AudioSuite Window Header : Selection Reference

Selection Reference
This menu aims the selected process at either clips selected in an audio track or playlist, or at clips selected in the Clip List.
When you select a clip on-screen (in either a track/playlist or the Clip List) Pro Tools normally selects both occurrences of the clip. Since you may not want to process both, this menu provides a convenient means of limiting the AudioSuite process to clips selected in one or the other.
 
Playlist
Applies AudioSuite processing to clips on the Timeline (playlists on audio tracks). Processed clips also appear in the Clip List.
Clip List
Applies AudioSuite processing only to selected clips in the Clip List. Processing is not be applied to clips on the Timeline (playlists on audio tracks).
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If the Use In Playlist option is enabled in addition to Clip List being selected in the Selection Reference pop-up menu, the processing will be applied to the selected clip in both the playlist and the Clip List.
AudioSuite Processing Clip Groups in the Clip List
AudioSuite plug-ins process Clip Groups in the Clip List with certain limitations. With audio files, AudioSuite processes are applied to all copies of a unique audio file in your session when the Clip List option and the Use in Playlist option are selected. However, when a Clip Group is selected for Audio Suite processing in the Clip List, Pro Tools does not recognize the Clip Group as audio. This is because a Clip Group is not treated as audio until it is actually used in a track. To apply AudioSuite processing to a Clip Group in the Clip List, first ungroup the Clip Group, and then regroup it after processing.
To apply an AudioSuite process to all copies of a Clip Group in a session at once, do the following:
1 Select the Clip Group to be processed.
2 From the Clip List menu, select Ungroup All. All elements of the group will remain selected.
3 Perform the AudioSuite processing.
4 From the Clip List menu, select Regroup.
When prompted, choose Modify to apply the AudioSuite process to all copies of the Clip Group in the session, or Copy to apply it only to the selected Clip Group.