[content warning: prosody]
I'm taking April off from Lorca. Since I can't exactly turn my brain off, I will be working a bit on prosody, with an eye toward my 2015 book project, a study of Spanish versification melding linguistic and literary perspectives, and integrating literary criticism and pedagogy, and addressed both to people who know Spanish and those who want to understand it from the point of view of English poetry.
Say the zero degree of metrical complexity is a situation in which the pattern wswswswsws... of the metrical pattern meets no resistance in its realization. I am thinking of lines like
"Of hand, of foot, of lip, of eye, of brow"
Each foot is a phrase, each strong position is a content word of one syllable, each weak syllable is a preposition, etc...
This could be a kind of metrical joke, in a way. Most lines in the stanza are obviously more complex:
Then, in the blazon of sweet beauty's best--
Of hand, of foot, of lip, of eye, of brow--
I know their antique pens would have expressed
Even such a beauty as you master now.
So the metrical pattern is not a metrical norm, from which complex lines deviate; rather, it is an abstract pattern of positions. Lines that exhibit no tension will be extremely rare, as a consequence. Because of the short phrases of the tensionless line, the effect is not even smooth or mellifluous, but, on the contrary, a deviation from the normal average degree of metrical tension. These lines are even more unusual in Shakespeare than lines of enormous complexity. Hence, paradoxically, a line of no tension will exhibit an aesthetic tension of a sort.
If we can formulate metrical rules in precise linguistic terms, then we can see that lines with a high degree of tension are not a matter of breaking rules, or introducing variations or substitutions, but of following the rules exactly while keeping an eye on the mismatches between metrical patterns and other linguistic factors.
[So to review briefly: metrical tension will be caused by:
Any kind of mismatch between the metrical pattern of swsw and phrasal boundaries, word boundaries; heavier syllables in weak position; lighter syllables in strong positions; the resulting stress clashes; enjambment, etc... Verse without a lot of complexity will be fairly dull, but by the same token fairly difficult to write, since a good degree of complexity is more natural. For the same reason, it is unnecessary to read verse aloud in a way that unduly emphasizes the metrical positions.]
Excepting the Dryden through Johnson period, most canonical English poetry in iambic pentameter tends toward a high degree of complexity, as in Donne, Shakespeare, Milton, Keats, or Yeats. Blank verse especially, and blank verse with a heavy degree of enjambment, even more. This blank verse tradition is one of the greatest poetic accomplishments I know of, comparable to the best Latin poet (Horace), and the development of the baroue sonnet in Spanish by Lope, Quevedo, and Góngora.