摘要:
Left- and right-hand keystroke windows X.sub.L and X.sub.H are decided in accordance with the positions of player's left and right hands pressing keys. When the number of pressed keys in either one of the windows X.sub.L and X.sub.H are larger than a predetermined value, that window is decided to be used as a chord identifying window, and on the basis of a combination of pressed keys in the chord identifying window, an accompaniment chord is decided for automatic accompaniment.