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This one is for @RichardAbbott who probably already noticed this:
I hadn't seen that video before but it's a great and truly geeky analysis! Thanks for letting me know
I suppose this metric is itself based on old Norse or Saxon rhyming schemes?
Well, Saxon ones (and Germanic in general) were not bothered about rhyme.
The standard for there was for lines to consist of two clear halves, each with two main beats, separated by a caesura (=short pause, think comma or maybe semi-colon). Within the line, alliteration of opening letters of words must be present, but end-rhyme is not important. Exactly which letters alliterate is subject to certain rules, especially around vowels (basically, imagine that vowels have the equivalent of Hebrew 'aleph before them, to give a consonantal beginning).
The first stressed syllable in the second half of each line must alliterate with either or both of the stressed syllables in the first half: the second stressed syllable in the second half is free.
Also, pronouns and such like are not alliterated, nouns usually are, verbs might be.
So a rather poor example might be:
Richard wrote: then ravening beasts
awoke in the land. Larger than dragons
yet with fleeter feet, their fiery breath quenched.
You might enjoy https://hugohouse.org/how-to-write-your-own-anglo-saxon-poetry/
Of course, the alliteration and whatnot is in the original, and translators differ widely as to how far they go to preserve it without sounding clumsy. Seamus Heaney's Beowulf goes a long way to preserving the swing of it, without trying to keep it on every occasion.
Colbert's analysis certainly has the two beats before and after a caesura, though Tolkien arranges them as separate lines rather than two halves of a line
Earendil was a mariner
that tarried in Arvenien
Colbert is also concerned with rhyme, especially internal rhyme, rather than alliteration.
I'm not so familiar with Norse forms and will do some looking around...
For Heaney, see for example http://www.pelister.org/courses/topics/beowulf/beowulf.pdf
A couple of lines early on shows him adhering to the pattern quite strictly:
There was Shield Sheafson, scourge of many tribes,
A wrecker of mead-benches, rampaging among foes
I'll note that the rhyme in Tolkien is on the leading syllables only - Ear; Mar; Tar; Ar. - would we call this a sort of alliteration?
Mariner doesn't rhyme with Arvenien.