GMC 2007 Yukon XL Owner's Manual page 306

Root Directory
The root directory of the CD-R is treated as a
folder. If the root directory has compressed audio
files, the directory will be displayed as F1
ROOT. All files contained directly under the root
directory will be accessed prior to any root
directory folders. However, playlists (Px) will
always be accessed before root folders or files.
Empty Directory or Folder
If a root directory or a folder exists somewhere
in the file structure that contains only
folders/subfolders and no compressed files directly
beneath them, the player will advance to the
next folder in the file structure that contains
compressed audio files and the empty folder will
not be displayed or numbered.
No Folder
When the CD-R contains only compressed files,
the files will be located under the root folder.
The next and previous folder functions will not be
displayed on a CD-R that was recorded without
folders or playlists. When displaying the name of
the folder the radio will display ROOT.
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When the CD-R contains only playlists and
compressed audio files, but no folders, all files will
be located under the root folder. The folder
down and the folder up buttons will search playlists
(Px) first and then go to the root folder. When
the radio displays the name of the folder the radio
will display ROOT.
Order of Play
Tracks recorded to the CD-R will be played in the
following order:
•
Play will begin from the first track in the first
playlist and will continue sequentially through
all tracks in each playlist. When the last track of
the last playlist has been played, play will
continue from the first track of the first playlist.
•
Play will begin from the first track in the first
folder and will continue sequentially through all
tracks in each folder. When the last track of the
last folder has been played, play will continue
from the first track of the first folder.
When play enters a new folder, the display will not
automatically show the new folder name unless
you have chosen the folder mode as the
default display. The new track name will appear
on the display.