Mary K. Savelli's discussion of Old English meter states that the first stressed syllable in the first half-line of an Old English poem must alliterate with the first syllable of the second half-line (she calls them--properly--the "a" and "b" half-lines). Actually either, or both, stressed syllables in the first half line may alliterate with the first stressed syllable in the second. At least one of them must alliterate.

To say this is not to suggest that the scop, or Old English poet, was observing schematic rules. Rather, what it tells us is that in the process of oral composition, the poet picked up the initial sound of one or both of the stressed syllables in the first half line, and repeated that sound as the initial sound of the first stressed syllable of the second half-line. Or, if we consider the entire line as an entity, the poet repeated the same initial sound on the third stress as had been used on the first or second, or both.