The interval between two adjacent notes in the pentatonic scale is a sophomore except for the small degree between the angle and the sign, the feather and the palace (a house with an octave high). In ancient China, it belonged to the Five Elements.
Another ancient book "Five Tones" is an article recorded in the ancient military work "Liu Tao", which is recorded in "Long Tao"-on military organizations. This paper introduces the method of observing and judging the enemy's situation with five tones and five elements.
It is almost absurd and unreliable to judge the enemy's situation according to the collocation of five tones and five elements, and even to command the use of troops. However, his idea of using various means to detect the enemy's situation, judging the enemy's situation through various clues and making corresponding decisions still has some merits. Nian Gengyao, the general of the Qing Dynasty, was warned by Yan Wen, which is one such example.