9. The musical score playing method according to claim 8 , wherein said changing further comprises changing the note values of the grouped notes when the playing time of the grouped notes is longer than the reference time of one beat and there is no note longer than the reference time within the group, or when there is a note longer than the reference time among the grouped notes and the playing time exceeds twice the reference time.
9. The musical score playing method according to claim 8 , wherein said changing further comprises changing the note values of the grouped notes when the playing time of the grouped notes is longer than the reference time of one beat and there is no note longer than the reference time within the group, or when there is a note longer than the reference time among the grouped notes and the playing time exceeds twice the reference time. 11. The musical score playing method according to claim 9 , wherein said changing further comprises changing note value for the number of grouped notes to a duration obtained by multiplying a total duration of the note values of the grouped notes by a number set in advance in accordance with the number of notes grouped.