Yueh Fu is one form of classical Chinese poetry, singable to the accompaniment of musical instruments. Over the years the music was lost, but the majority of the lyrics of Yueh Fu have been preserved. Tzu-yeh ko (Songs at Midnight) were the most popular folk songs during the Six dynasties (222-589 A.D.). This set of stamps includes four of the Tzu-yeh songs of the four seasons of a year. They describe nature as well as daily life. The four pieces of Yueh Fu that appear on the stamps were selected by Professor Ching-ping Yeh of National Taiwan University.