高僧傳 13.56

13.56

論曰：夫篇章之作，蓋欲申暢懷抱，褒述情志。詠歌之作，欲使言味流靡，辭韻相屬。故〈詩序〉云：情動於中，而形於言。言之不足，故詠歌之也。然東國之歌也，則結韻以成詠；西方之贊也，則作偈以和聲。雖復歌讚為殊，而並以協諧鍾律，符靡宮商，方乃奧妙。故奏歌於金石，則謂之以為樂；設讚於管絃，則稱之以為唄。

The appraisal states: Compositions in prose and verse are meant to express inner feelings and praise emotional sentiments. Chanting and singing are meant to make the aesthetic flavor of words flow smoothly and link rhyme and diction together. Therefore, the "Preface to the Book of Songs" says: "Emotions are stirred within and take form in words; when words are insufficient, one sighs and sings them." Yet the singing of the Eastern lands forms chants by weaving rhymes, whereas the hymns (stotras) of the Western lands compose verses (gāthās) to harmonize the sound. Although singing and hymns differ, both must harmonize bells and pitch-pipes and conform to the pentatonic scale to achieve profound subtlety. Therefore, when singing is performed on metal and stone, it is called music; when hymns are set to pipes and strings, it is termed chanting (bhaiṣajya/stotra).