In an electronic music apparatus system, a unique musical instrument ID is stored in an electronic musical instrument by means of a plant computer before shipment thereof. After purchase of the electronic musical instrument, a user transmits the stored musical instrument ID to a management computer via a network without use of any intermediate device or by use of a user computer or a user portable communication terminal and performs user registration. By use of the musical instrument ID, the user downloads a program or content item suitable for the electronic musical instrument from a program distribution computer or a contents distribution computer via the network.