The Song dynasty was renowned for a less rigid style of poetry than Tang poems, called "prose-poetry" (詞).
For a literary comparison of Tang poems and Song prose-poems, here is an excerpt from an essay by Qian Zhongshu (錢鍾書), written primarily as a foreword to C. D. Le Gros Clark’s translation work "Su Tung-po’s Prose-Poems":-
"Chinese poetry, hitherto et…