It needs to be a FAT32 drive not NTFS for an 83...you need to select "Music" from the home menu not any of the other options, e.g. "Movies" as it only shows Movie files under Movies.
Also note from the manual:
The USB ports are rated to provide a maximum of 5V, 500mA power to the
USB drive. It is sufficient for all USB thumb drives and flash memory card
readers, but may not be sufficient for USB hard disks.
• This unit supports “USB Mass Storage Class Bulk-Only Transport” devices only. Most
USB thumbs drives, portable hard disk drives and card readers conform to this device
class. Other USB devices such as MP3 players, digital cameras, and mobile phones
may not be compatible.
• Supported USB drives must be formatted with the FAT (File Allocation Table) or FAT32
file system. Drives formatted with NTFS file system are not supported.
• In some cases, an incompatible USB device may cause the player to stop responding. If
this occurs simply turn off the power, remove the USB device, and turn the player back
on.