在宋代政治史的研究領域之中，樂制的整理與考察，較之其他制度稍顯薄弱。北宋朝廷在一百餘年中進行了六次較大規模的樂制改革，究其原因、過程及影響，與宋代獨特的政治、文化環境關聯緊密。在宋樂的「六改作」之中，仁宗景祐時期以「李照樂」為中心的改革，產生了與以往不同的內容與意義。李照批判太常舊樂、確立自創新樂的理據、與馮元等人圍繞「四清聲」展開的論辯、新樂先被支持繼而取締的緣由等，構成了景祐樂制改革的核心內容。它一方面令樂律理論的合理性、合法性論證成為改革的主題和成敗的標準，使士大夫的議論從此圍繞「樂理」的核心展開；另一方面，突出了樂與政、政治的現實與理念之間的關聯互動，展現出仁宗初年政治文化的複雜性：重古、疑古，法古、變古，由古器而溯今，由古道而治今，恪守漢唐傳統、祖宗制度與回向三代之政治追求、反變革與變革之間充斥著不同向度的角力。毫無疑問，在景祐「李照樂」之論爭中，我們看到了宋代政治、文化及其政治文化的一場富含深意的「變革」。

The Northern Song imperial court presided over six large scale reforms of the music system, causing debate between different groups both in and out of court. The reasons behind, process and effect of these reforms were closely related to the distinctive cultural and political circumstances of the Song dynasty. Of all these reforms, those implemented between 1034 and 1038 were unprecedented in substance and significance. The core of the reforms centered on Li Zhao’s 李照 music: his criticisms of the old music system handled by the Court of Imperial Sacrifices (the official department managing music-related affairs); the basis of his new theory of music; the debate between Li and his opponents; and the reasons why his new theory was at first supported, then subsequently banned. This established proving the rationality and legality of music theory as the theme of reforms and the standard for measuring their success or failure, defining the focus of subsequent debates among scholar-bureaucrats. It also highlights interaction between music system and polity and the connection between political theory and reality, revealing the complexity of the political culture.