An object of the present invention is to allow a client to make a request for music data stored in a server and to receive it and play it back. A client program 421 controls the sending of a request signal to a server 401, the reception and playback processing of music data from the server 401, and the display of a GUI performed by a display controller 426, and outputs the music data received by a communication unit 423 from the server 401 to an audio data converter 424. A server program 411 controls the sending of music data to the client 402, and registration of information in a music database 415, a link information database 416, and a ranking information database 417, searches the music database 415 for the requested music data, and sends the music data to the client 402. The present invention can be applied to a personal computer, a PDA, a cellular telephone, a desk-top playback device, a portable playback device, and a simplified playback device.