To musical composition information such as a standard MIDI file, there are added accessory data, such as message or text data, and setting information for the accessory information which are both unrelated to the musical composition information. These accessory data and setting information are inserted, as meta events, in the standard MIDI file. In this way, a musical composition information file can be created which is an integral combination of the musical composition information and the accessory data containing the setting information. The musical composition information file with the accessory data can be transmitted or received via a communication network, or stored in a recording medium for portability. The musical composition information file can be reproduced to permit simultaneous execution of performance reproduction processing and image reproduction processing such as for display of a message.