It is clear that in writing in couplets, however metrically "rough," Spenser was broadly coming much closer to the forms of the poets he was closely imitating and translating into English, who wrote stichic
poetry that is grouped in irregular verse paragraphs, not stanzas.
I have surveyed a variety of rhapsodic games, arguing that rhapsodes were competent at many levels of poetic performance: they could, for example, competitively recite memorized verses, improvise verses on the spot for elaboration, take up and leave off the narrative wherever they saw fit, as well as perform stichic
improvisation in response to questions, riddles, etc.
The final verse foot is always HH, which follows from the fact that the final metrical position is H in all stichic
meter (ANCEPS), and it is likely that this puts pressure on the preceding foot not to end in a H.
The terms used to describe the epic melodies, their modality, scale structure, cadential endings, motivic, stichic
, strophic, or stanzaic forms, are borrowed from art music; they are not known to, nor do they have any meaning for the singer.
That is, whether it's quatrains, tercets, stichic