Reference answer:

Pinyin: lù m ù y ù ng mù, abbreviated as lmym.

Idiom explanation: green horse: that is, green ear, the name of ancient good horse; Yang: Face up; Feed the horse. The horses facing the feed all looked up and refused to eat. Describe the wonderful music, even the horses stopped to eat and listen.

Idiom origin: Tang Wang Ji's "Boya plays the piano and praises Zhongzi": "The green horse starts, and the Dan fish shrugs."