culled, quoted, inspired by, and paraphrased from John Ciardi’s classic How Does a Poem Mean?
The mechanical pattern of a poem is the exact, standard, normal beat, as if a metronome were counting out the beats. But poems written in strict mechanical pattern are boring and flat, as is music played strictly by the metronome. The ways the mechanical patterns is stretched, broken, surprised, are all ways that the performance of music and of poetry take on personality, emotion, and meaning.
It is useful to think of the pattern of mechanical iambic pentameter as roughly corresponding to the squares on graph paper: the variations of the drawn graph are meaningful only as they work against the fixed norm of the squares. In poetry the mechanical pattern may be thought of as an expectation. The metric performance of any line happens in the way it works its variations against the established expectation. Ciardi page 923
Common Ways to Work Against the Pattern
1. slipping in extra unaccented syllables
2. displacing an expected accent, as in the reversed foot
3. by increasing the number of stresses, primarily by the use of spondees and monosyllabic feet
4. by grouping stressed or unstressed syllables
5. by the manipulation of internal pauses (caesura), end-stops, and run-ons