The complex relationships between written and spoken literature in some societies can make this definition hard to maintain.
In most oral literature, poetry is defined by the fact that it conforms to metrical rules; examples of non-poetic oral literature in Western culture include some jokes, speeches and storytelling.
This theory showed how stock phrases could enable poets to improvise verse.
Examples of orally improvised poetry are the epics of the Serbo-Croatian guslars studied by Parry and Lord, Basque bertsolaritza, and freestyle rap.
Prominent examples of memorised oral poetry are some nursery rhymes, ballads and medieval Scandinavian skaldic verse.