在音乐中，调性这一概念十分重要，如果你还在演奏调性音乐，那么调性理论系统的重要性，就堪比生活中知道你走路的GPS，因此本app专门为调性学习者而来。
本app可以作为教师讲授“调性”知识点时的教具，亦可作为学生自主学习音乐“调性”知识点的学习器。
Tonality is very important in music, such as gps on your road.If you still play tonal music, maybe you will need this app.
This app could be a teaching aid when teachers teach tonality, and it also could be a learning device when student learn about tonality.