What are the innovations of poets in Song Dynasty?

Three poets in the Northern Song Dynasty made bold changes in the development of Ci. The first two are:

First place, Liu Yong. As soon as Liu Yong changed his words, he pulled them out of the boudoir, and the lyric hero of the words was no longer a homesick woman in the boudoir, but an ordinary person; He adopted the new voice of the market, so "where there is a well, you can sing Liu Ci." He also created a long tune of slow words, which changed the traditional style with Xiao Ling as the absolute theme.

Second place, Su Shi. Su Shi is the second all-round genius to "transform" Song Ci. He broke through the barrier of the word "Yan", applied the expression method of poetry to the field of ci, gradually poeticized the content of ci, expanded the theme of ci, created a bold style of ci, and pushed ci to a new historical stage.