Note
乐 is read yuè (music) here, not lè (happy).
礼乐 is a foundational Confucian concept:
礼 (ritual / propriety) governs hierarchy and conduct,
乐 (music) harmonizes hearts and emotions. Together they were the Duke of Zhou's (
周公) system for ordering society, idealized by Confucius and central to texts like 《
礼记》 (Lǐjì, 'Book of Rites').