I just finished reading Timothy Steele’s excellent book on prosody, all the fun’s in how you say a thing. I can’t recommend it highly enough to anyone interested in writing or reading metrical verse. Reading through the table of contents, I had some initial misgivings about, for example, a 35-page chapter on the history of elision; but it turned out to be a gripping read.
One of the main lessons I took away from the book was not to think about metrical stress as a binary on/off, but as a range of numerical values. Steele suggests 4 as a handy number, but you could think about it as a musical scale or any range of intensities. An iambic foot should always have the second beat stronger than the first, but emphasis between feet can vary up and down like a mountain range. He gives this line as an example, where the last 4 beats he would assign stress levels 1-2-3-4, so the weak beat of the last foot is stronger than the strong beat of the penultimate foot: “Drink to me only with thine eyes”. As well as the initial trochaic inversion, the varying stress strength gives the line its driving shape.
People who dislike metrical poetry often see it as a plodding kettle drum – da dum da dum da dum da dum da dum — but the English language is more melodic than that. Cadences rise and fall and vary like a tune, but meter provides the overall beat. Free verse likes to dispense with that, but the result often strikes my ear like Spinal Tap’s Freeform Jazz Odyssey. So very modern. So very dated.