Just as in a supermarket, where the person at the check-out28 no longer needs to engage in29 any mental arithmetic30, so a composition student31 may not really know how you form a dominant seventh chord32 if all he has to do is hit a command key.

• 就像超市的收银员不再需要任何心算一样，学作曲的学生可以不必真正懂得如何构成属七弦，因为他只需要点击一下指令键。