There is input type information defining a type of portable terminal as well as various music composing parameters. Automatic music composition process is carried out on the basis of the input type information and music composing parameters, so as to generate musical composition data suitable for reproduction on a portable terminal of the type indicated by the type information. Balance in predetermined musical characteristics of the generated musical composition data can also be achieved by adjusting the predetermined musical characteristics in accordance with the type of portable terminal. It is also possible to convert the generated musical composition data into a predetermined data format suiting the type of a portable terminal to be used. The generated musical composition data may be transmitted online to the portable terminal.