-D: Add new audio files to the database.
-U: add [-l] [-f] [-v] path...
-H: Each given path may be either the full path to an audio
-H: file, or the full path of a directory. In case of a
-H: directory, all audio files in that directory are added
-H: recursively. Only absolute paths are accepted.
+D: Add or update audio files.
+U: add [-a] [-l] [-f] [-v] path...
+H: Each path must be absolute and refer to either an audio file, or a
+H: directory. In case of a directory, all audio files in that directory
+H: are added recursively. Only absolute paths are accepted.