鸿雁老去笛声不续
[hóng yàn lăo qù dí shēng bù xù]
The phrase implies the melancholy and nostalgia felt over lost time or missed opportunities. 'Hóng Yàn' (wild goose) symbolizes messages or letters, conveying feelings of departure or change, while 'dí shēng bù xù' suggests the cessation of joyful melodies played on the flute, evoking a sense of loss and regret.