Keep calm :D EXACTLY what I'm preparing for Omentielva!

I'm trying to hunt down where the idea of "long and short vowels" comes from, but am failing. My guess is that it means "a long series of short verses", looking at what Aragorn calls "Ann-thennath" in LotR. It's my guess that a Beleglin is an epic made of songs composed in the Ann-thennath mode.

I tend to lean towards accentual verse - it was a form used in Old English, and it would separate Ann-thennath from Minlamad (which I personally take to be alliterative verse with a caesura). It would however also mean the two are rather closely linked (not necessarily a bad thing) as obviously Beowulf was written in an alliterative form of accentual verse (I'm picking Beowulf because it and Tolkien are well linked).

Fyi, Wynne and Hostetter have an article "Three Elvish Verse Modes" in the Tolkien's Legendarium collection, analyzing ann-thennath, minlamad thent/estent, and linnod.