The oldest one was stated by Kenko YOSHIDA in "Tsurezuregusa" (Essays in Idleness), which mentions that Shinano no Zenji (former official from Shinano) Yukinaga is the author of Heike Monogatari, and he taught the tale to a vision-impaired musician called Shobutsu to have him narrate it.
最古のものは吉田兼好の『徒然草』で、信濃前司行長（しなののぜんじゆきなが）なる人物が平家物語の作者であり、生仏（しょうぶつ）という盲目の音楽家に教えて語らせたと記されている。