The sentence in "The Analects of Confucius" that expresses the appreciation of music to the point of forgetfulness is: When Zi heard "Shao" in Qi, he didn't know the taste of meat in March.

Original text: When Zi heard "Shao" in Qi, he did not know the taste of meat in March. Said: "It's not just for the sake of pleasure."

Translation: Confucius listened to "Shao Music" in Qi State and ate meat for a long time without realizing the taste. He said: "I didn't expect good music to be so charming."