In modern, written poetry, we often judge the excellence of the creator by the use of unusual but appropriate imagery. The more original the poem is, the better. The bards who performed in the oral-formulaic tradition, however, were evaluated for the skill with which they could weave together familiarphrases in that poetic tradition in order to tell a story that was either already known to the audience or that was an extemporaneous effort by the scop (a traveling bard).
The poet's apprenticeship would have included learning certain traditional themes, popular stories, names of various characters, and the formulas through which the bard eventually performed the tales or created his own stories. We might expect a performer to be able to fit the theme of the piece, and even the length, to a particular occasion, as Hrothgar's scop does in Beowulf. The more accomplished bard would be the one who made most effective use of the common arsenal of formulas. A popular piece might be presented over the course of two or three or more evenings.
If a poet happened upon an especially effective formula of his own, the phrasing would become part of the oral-formulaic lexicon. Borrowing images or phrases from each other was accepted and expected. Francis P. Magoun, Jr., a noted Beowulf scholar, closely examined the first 50 verses of Beowulf and found that approximately 70 percent appear entirely or in part in other Anglo-Saxon poetry, even though there were only about 30,000 lines of Old English poems available for comparison. Magoun maintains that virtually all of the phrasing could be found elsewhere if we had a larger body of Anglo-Saxon works.
This clearly alters how we look at the "authorship" of the poem. Some scholars suggest that the person who put together the extant version of Beowulf was no more than an editor or organizer of poems created by others, probably over generations. Others credit the poet with considerable creativity while welcoming the evidence of oral tradition. It may be that a trained scop dictated the work to a scribe or that the poet had become literate, probably educated at one of the monasteries that existed in England at the time, which could account for the Christian influences in what probably was originally a pagan poem. Whatever the method was, the excellence of the work implies that the final result was the product of one very talented poet.