A musical score processing method that is realized by a computer includes receiving a control data related to displaying of a musical piece from a music processor that executes a process related to the musical piece and that is realized by a music processing program, using inter-application communication, based on a musical score processing program, and executing a display control process by displaying a musical score of the musical piece on a display device and controlling the displaying in accordance with the control data that has been received, based on the musical score processing program. The music processing program is separate from the musical score processing program.