The difference between adding an audio file and copying an audio file in Pro Tools is that:

The correct response is that adding references the audio file in its original location. When you choose to add an audio file in Pro Tools, the program simply creates a session reference to the file without moving it from its initial location on the drive. This means that the audio file remains where it is stored, and Pro Tools accesses it directly from that location. This is particularly useful for conserving disk space since the audio itself is not duplicated; instead, you are working with a link to the existing file.

In contrast, copying an audio file involves creating a duplicate of the original file, which takes up additional storage space and results in an independent copy that can be moved around within the session without altering the original audio file. Understanding this distinction is essential for effective file management within Pro Tools, especially when organizing large projects with numerous audio files.