Dear Victoria
First, let me apologise for the delay in responding to the questions you raised. The past few days have been unexpectedly busy, and this is the first chance I have had of reflecting on them. In fact, I think Alicia has really answered for me, and I am happy to concur in her remarks; but let me add a few further comments.
The briefest but also, really, the fullest answer I can give is to recommend Derek Attridge’s fine book
Poetic Rhythm: An Introduction (Cambridge, UK: Cambridge University Press, 1995). In my view, this is the best account of the way accentual metres (which he calls stress metres) and accentual-syllabic metres operate, including the way they are derived from the naturally occurring phonetic patterns of English. My own views on metre coincide almost entirely with Attridge’s. I have mentioned this book on a number of other occasions and posted a short description of it at
http://www.ablemuse.com/erato/ubbhtm...L/000259.html. In particular, chapter 4 deals with the issues you mention.
As to what I called "rhetorical" stress, here, once again, are my remarks about Kevin’s line: "The first line of the eighth quatrain has only four beats: "But, d
amn art! P
oetry w
ill hold sw
ay". You perhaps meant the line to go like this: "But, d
amn
art! P
oetry w
ill hold sw
ay". But this is to rely on a
rhetorical emphasis not inherent in the
metre. Metrically, "art" is demoted and does not carry a beat."
I am sorry if this is unclearly expressed. As Alicia says, there is a powerful and, as it were, a natural tendency in ordinary non-metrical speech to downplay the stress on the middle of three syllables which would, in other contexts, attract stress. In the case of Kevin’s line, it is possible to overcome this natural tendency by forcing an emphasis on to "art", and it is this kind of forced emphasis I am referring to as "rhetorical emphasis" - "rhetorical" because it is an emphasis which one might in delivery choose to add in order to bring out a particular nuance. Such an emphasis is not, however, part of the metrical structure and is not required by the metrical structure. One of the beauties of metre is that the pattern of beats, the metrical pulse, partly subdues and partly draws out the naturally occurring stresses of the language. I think Alicia is making rather the same point when she remarks that "meter should help readers with their footing rather than trip them up".
Accentual metres are arguably harder to bring off successfully than accentual-syllabic metres. The reason lies in the fact that one may admit more unstressed syllables and require the accommodation of more stressed syllables in positions which do not demand a metrical beat than is usual in accentual-syllabic meters, where the line is additionally constrained by the need to keep quite close to a particular number of syllables per line (between nine and about twelve, for instance, in IP). If the line is stretched too often or in a careless way, the regular pulse, the regular pattern of metrical beats, on which both metres depend may be endangered. It is at such points that a special difficulty arises for the poet. As writers, we hear the words we are working with in a certain way. This can exercise such a mesmeric power over our ear that it is easy to become wedded to that one way of hearing them and fail to notice that another reader, who cannot hear how we choose to read the words, might well detect a different pattern. In such cases, one might say that the control exercised by the metre over the shape of the language has become too lax, leaving the independent reader metrically adrift, something which the stricter demands of accentual-syllabic metres make less likely. In such cases, if the reader could only hear the poet read the lines out loud, the intended pattern would become apparent; but to the extent that the intended pattern was not made inevitable by the management of the metre, one might want to call such lines defective.
Best wishes!