《太平广记·卷二百零三·乐一》
到了祖孝孙创造旋宫之法后，十二钟都扣，再没有悬在那里不扣的了。
及孝孙造旋宫之法，扣钟皆遍，无复虚悬矣。
After Zu Xiaosun created the method of rotating the palace, all the twelve bells were beaten, and there were no bells hanging there without being beaten.