Studies of orality as such have brought out that oral narrative is not always put together in terms which admit of ready structuralist binary analysis, or even of the rigid thematic analysis which Propp (1968) applies to the folktale. The structure of oral narrative collapses at times, though this fact does not hamper a good narrator skilled in digression and flashback techniques. The straightforward narrative 'line'Š is much less operative in primary oral performance than in written composition (or in oral performance by persons influenced by written composition). Oral composition works with 'informational cores' in which the formulas do 'not show the degree of organization that we commonly associate with thought', although the themes do so more or less.
Walter J. Ong, Orality and Literacy: The Technologizing of the Word, 164-5