What is the technique of "saying other things first, giving speeches and singing" and what is it called in poetry expression?

The technique of "talking about other things first to arouse the recited words" is called "xing" in poetic expression, which is one of the six meanings of the Book of Songs. Zhu said in Biography of Poems: "If you are interested, say something else first to arouse the recited words." It is somewhat similar to the technique of "Chinese cabbage, yellow heart, no mother at three or two years old". Originally, I wanted to write about the loss of my mother, but I said Chinese cabbage first to lead to the theme of singing.