It records that Nakrang had a sacred drum and trumpet that sounded by themselves in case of foreign invasion called the Jamyunggo.
Their southern neighbor country, Nakrang, was in a better geographic location for farming and fishing, which was crucial for their growing population.
Although Goguyeo was tremendously stronger in military power, Nakrang's Jamyunggo was a great concern for King Daemusin.
Nakrang owned a mythical drum and flute, Jamyunggo, that played themselves when an enemy approached, which served as a heavenly protector for the country.
The King was aware that the expanding Goguryeo was a brutal country with a base of strong military power and feared they would be the next target.
The author, Kim Busik, published this compilation to address the growing disconnection between the history and the people.
Also, the chronicles were compiled to illustrate a stricter Confucian doctrine, intended as a keystone to order family relationships and govern the state.
[5] Therefore, it is not clear if this legend of a Jamyunggo (자명고), i.e., of a Self-beating drum, was a part of the former Goguryeo's Sinjip, or some "original research" added by Kim Busik to illustrate the Confucian influence.
[6] This Korean counterpart of the Romeo and Juliet story has been largely used nowadays as a source of inspiration by various artists and essayists.