A peripheral device in which a large number of cartridges or reels of magnetic tape are stored in cells in a storage matrix. Any chosen cartridge can be transferred mechanically to a tape transport where it can be accessed by the host system, and then returned to the same or another cell. The device also contains one or more drawers that can also be reached by the transfer mechanism: these are accessible to an operator so that cartridges can be introduced to or removed from the library.