《北史·列传·卷三十七》
斛斯征说 ：《孝经》上说 ：父母丧，听到音乐也不高兴。 
徵曰： 《孝经》云 闻乐不乐。 
Yu Si Zheng said: "The Book of Filial Piety states: When parents are in mourning, one does not find joy in music."
<s>[INST] Identify the key themes in this Classical Chinese text and explain them in English: 徵曰： 《孝经》云 闻乐不乐。  [/INST] Yu Si Zheng said: "The Book of Filial Piety states: When parents are in mourning, one does not find joy in music."</s>
Identify the key themes in this Classical Chinese text and explain them in English: 徵曰： 《孝经》云 闻乐不乐。
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Yu Si Zheng said: "The Book of Filial Piety states: When parents are in mourning, one does not find joy in music."
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