To make it possible to analyze the music structure of inputted musical performance information and give an accompaniment pattern matching the music structure of the musical performance information corresponding to the analytic result.

A data supply means supplies melody data constituted including at least pitch and sound length. The melody data is continuous progression of note data consisting of pitch and sound length. In the music world, music is completed generally according to a flow of scenes represented like 'A-A'-B-C', etc. A music structure analyzing means analyzes the music structure from the melody data and divides the melody data into plural sections according with the said flow of scenes. A rise degree calculating means calculates the rise degree of each of the divided sections and analyzes the flow of scenes of the respective sections of the melody data according to the calculated rise degrees. The rise degrees numerically represent the upsurge of emotion of the music and the flow of the scenes that the music has can easily be grasped according to them. Further, desired accompaniment patterns are allocated to the respective sections according to the analytic result, i.e., the rise degrees of the respective sections to automatically arrange the music according to the flow of the scenes that the music has.