A CPU sets an application of music sound generation to each of plural ports, and a priority to the set application, and further sets the maximum number of channels that assign an arbitrary sound source to each port from plural kinds of sound sources and produce sounds. When a new sound generation request is supplied to a certain port in which all sound generation channels of the port are currently generating sounds, and when the sound generation channels to be used for the sound generation are in short, the CPU supplies the sound generation request to a channel not producing a sound currently in other port to which the application of the same priority is set.