The birds are startled when the moon rises, and the springs are singing. The birds' "coming out" and "startled" and "singing" are touching and audible, but the effect is not noisy, but powerful.
Ground contrast "people are idle", "night is quiet" and "mountains are empty"
Or the dialectical relationship between phenomenon and essence.
These two sentences reflect the same philosophy.
You can ask me if you don't understand.
Philosophy needs experience and a certain literary background.