The oral-formulaic method is a formula of repetition used by oral epic singers to allow for more fluent composition and memorization.
From A Poet’s Glossary
The following definition of the term oral-formulaic method is reprinted from A Poet's Glossary by Edward Hirsch.
Milman Parry (1902–1935) and his student Albert Lord (1912–1991) discovered and studied what they called the oral-formulaic method of oral epic singers in the Balkans. Their method has been variously referred to as “oral-traditional theory,” “the theory of Oral-Formulaic Composition,” and the “Parry-Lord theory.” Parry used his study of Balkan singers to address what was then called the “Homeric Question,” which circulated around the questions of “Who was Homer?” and “What are the Homeric poems?” Parry’s most critical insight was his recognition of the “formula,” which he initially defined as “a group of worlds which is regularly employed under the same metrical conditions to express a given idea.”
The formula revised the standard ideas of “stock epithets,” “epic clichés,” and “stereotyped phrases.” Such often repeated Homeric phrases as “eos rhododaktylos” (“rosy-fingered dawn”) and “oinops pontos” (“wine-dark sea”) were mnemonic devices that fitted a certain metrical pattern and aided the epic singer, or aiodos, in his extemporaneous composition. Such phrases could be substituted and adapted, serving as placeholders, as a response to the needs of both grammar and narrative. These formulas, which could also be extended, were not particular to individual artists, but a shared traditional inheritance of many singers. Parry’s work revolutionized the study of the Homeric poems by treating them as essentially oral texts. For example, Parry and Lord observed the same use of formulas in Serbian oral poetry that they found in the Homeric poems.
Parry and Lord discovered that the epic form was well-suited to the singer’s need for fluency and flexibility, for composition as well as memorization. The singers composed poems orally by calling upon a rich storehouse of ready-made building blocks (traditional patterns), which moved well beyond phrasing. Singers could call upon this stock of lines and formulas for describing places, expressing different characters, and narrating action — and thus perform epics of 10,000 lines or more with uninterrupted fluency. Parry and Lord provided us with a generative model of epic performance. F. P. Magoun explains that oral poetry is composed “rapidly in the presence of a live audience by means of ready-made phrases filling just measures of isochronous verse capable of expressing every idea that the singer may wish to express in various metrical situations.” The oral-formulaic method has subsequently been applied to a wide variety of texts and genres, such as Babylonian, Hittite, and Anglo-Saxon epic poetry; medieval romances; Russian byliny; the corpus of pre-Islamic poetry; Toda ritual songs; Coorg dance songs; English and Spanish ballads; and even African American revivalist sermons. Oral formulas also clearly influenced written poetry. It is now possible, for example, to view Old English poems as transitional texts, written poems that embody oral formulas.