Reminds me of something I read about Hindu scriptures and mythology from ancient times. None of them got written down until like 2nd Century BCE, meaning they were passed down orally from teacher to student despite being grotesquely long

For example The Mahabharata consists of over 200,000 individual verse line and long passages written in prose. The Ramayana is 24,000 verses.

Apparently the priests chant these verses in a very specific style of song/prayer and over time these get ingrained in the students heads. It’s the pattern and rhythm that really helps with memorization.

Therefore all the Hindu texts are preserved with almost perfect grammatical and tonal fidelity, to the point where we can easily learn the ancient Sanskrit language without much guessing or reconstruction