oral epic
A long narrative poem, originally transmitted orally, recounting heroic deeds and events of cultural significance.
The Tale of the Heike was originally passed down as an oral epic.
叙事詩 is a broader term for any epic poem, while 伝承叙事詩 specifically emphasizes oral transmission and traditional storytelling.
Compound of 伝承 (oral tradition) and 叙事詩 (epic poem). The exact historical derivation is uncertain; the term is a modern academic coinage.