In the warring State Period (zhàn guó 战国) , there was a girl in the State of Qi called Han E (hàn é 韩娥) who sang beautifully. Once when she was passing through the State of Qi she had to sing to earn money to buy food. When she left Qi the echoes of her songs clung to the beams of the houses there for three days before people realized that she had left.
This idiom is used to describe unforgettably beaurifull singing.