In this section, as before, I will not be directly describing the structure of the older alliterative form, in this case the form deployed in such works as Sir Gawain and the Green Knight. Instead, I will be describing how I personally believe that the Middle English form works, but focusing as before on describing how to produce similar verse in Modern English.
Here, as before, I will not be presenting current scholarly theories of Middle English alliterative meter (though the account I will present has been heavily influenced, among others, by the work of Thomas Cable, Hoyt Duggan, and R.D. Fulk. The hypothesis I am going to present may be defensible with respect to Middle English, though I am not in a position to justify the argument technically in terms of the historical evidence of Middle English sound patterns, but it works extremely well in producing alliterative verse similar in sound and feel to the Middle English text, and was developed in large part to give me a rigorous metric during my ongoing work translating Sir Gawain and the Green Knight.
I would contend that there is, essentially, one difference, and one difference only, between the Middle English and the Old English alliterative meters. In my view, in the Old English meter, double alliteration on the first half-line is purely optional, whereas in the Middle English meter, it is the metrical norm. Everything else follows from this one difference.
In the terminology I developed in the previous sections of this discussion, we could put the difference like this: all Old English half-lines contain one pivot, even if there is incidental alliteration on the second major stress in the first half line. In the Middle English form, the norm is two pivots in the first half-line, and one in the second. Consider, for instance, the first several lines of Beowulf. I have highlighted the pivots:
Hwæt! We Gardena in geardagum,
şeodcyninga, şrym gefrunon,
hu ğa æşelingas ellen fremedon.
Oft Scyld Scefing sceaşena şreatum,
Only the fourth line has double alliteration in the first half-line. Of course, there are many, many, many lines in Beowulf where double alliteration is present, but the norm is that only one alliterating syllable is necessarily present, and thus that there is only one pivot. A consequence is that the rhythmic patterns of the Old-English half-line are very strongly constrained, for every other syllable in the half-line must be rhythmically subordinate to the pivot.
Now contrast the first four lines of Sir Gawain and the Green Knight. Once more the pivots (as I would analyse them) are highlighted:
SIŞEN şe sege and şe assaut watz sesed at Troye,
Şe bor3 brittened and brent to bronde3 and askez,
Şe tulk şat şe trammes of tresoun şer wro3t
Watz tried for his tricherie, şe trewest on erşe:
All four lines have double alliteration in the first half-line, and while exceptions occur, the overall feel is very different. And it corresponds to a profound rhythmic difference, which can be measured simply by counting syllables. Only one of the first four initial half-lines of Beowulf has six syllables, and that is a line with resolution, whereas none of the first four initial half-lines of Sir Gawain and the Green Knight has less than six syllables, no matter how one resolves various questions about the pronunciation of the Middle English. In the account I have developed on this website, there is a very simple explanation: if the Middle English form follows the norm that there are two pivots in the first half-line, there is considerably more room for rhythmic variation. Extra syllables can be included in the first half-line, as long as they are subordinate rhythmically to one or the other of the pivots, and as a result there is a considerably greater freedom of rhythms in the first half-line, whereas the second half-line, with only one pivot, much more closely resembles the Old English rhythm.
Following these rules has worked well in my Sir Gawain translation, and also works well in various other poems I have tried to write in the Gawain form. For instance, in the fantasy novel I am currently collaborating on, there is an embedded bit of alliterative verse, in which the following lines appear:
Disease, plague and pestilence are perils that fall
like mist in the morning. As the mourners dream,
dawn creeps uncalled-for over clammy cheeks,
over face and forehead freckled with sweat.
Neither courage nor cowardice count when such foes
batter at bone or at burning flesh.
Notice how the first half-line can contain rather more than the second. For instance, the half-line disease, plague and pestilence has the rhythmic structure shown below:
This line contains two heavy dips, which could never work in an Old English half-line, nor in the second half of a Middle English line, but is quite consistent with the very free metrical patterns of Middle English, which I would argue do not particularly care what arrangement of stresses occur in the first half-line as long as the two alliterated pivot syllables are metrically more prominent than everything else.