Ecchu no kami (Governor of Ecchu Province) at that time was OTOMO no Yakamochi, and so Hirotada is thought to have made a written record of waka under Yakamochi, which turned into "Manyoshu" Volume 18.
そのときの越中守が大伴家持で、広縄は家持のもとで歌の筆録を行ったと考えられ、それが『万葉集』巻18となった。