When Emperor Xuanzong offered sacrifices at Mount Tai in 725 , Liu Yan , then a child , wrote a song .
When Emperor Xuanzong offered sacrifices at Mount Tai in 725 , Liu Yan , then a child , submitted it to Emperor Xuanzong .
When Emperor Xuanzong offered sacrifices at Mount Tai in 725 , Liu Yan , then a child , wrote a song and submitted it to Emperor Xuanzong .