觀無量壽佛經疏 3.66

3.66

五、從又有樂器下，至不鼓自鳴已下，正明樓外莊嚴。寶樂飛空聲流法響，晝夜六時如天寶幢，無思成自事也。

Fifth, from "Moreover, there are musical instruments" down to "sound by themselves without being struck," it directly explains the adornments outside the towers. Jeweled musical instruments fly in the air, their sounds broadcasting the resonance of the Dharma during the six periods of day and night, like the jeweled banner of the devas, spontaneously accomplishing their own tasks without thought.