But does the remembering of long, complex songs require the same skills as composing them?

To take a very different sort of case, Parry and Lord's guslars (a tiny minority of the population, IIRC)could create small epics almost on demand, but they weren't stanzaic and didn't rhyme, features which add complexity and tax concentration even more.

I'm not suggesting, of course, that illiterate people didn't have talent, especially when most of the population, including the mute inglorious Miltons, was illiterate. It's just that the more artistically satisfying songs (including most of those that eventually led us here) are very likely to have been composed, or extensively overhauled, by the more rather than the less sophisticated members of the community.

I vaguely recall that David C. Fowler suggested similar ideas many years ago, but memory is hazy.