The traditional typology of English poetic meters makes a binary division between strong-stress (or accentual) meters and accentual-syllabic (or syllable-stress or syllable-accent) meters. According to this typology, Old and Middle English alliterative poetry was composed in strong-stress meter; the iambic pentameter from Chaucer to Yeats and on to the present has been an accentual-syllabic meter. Intersecting with this literary typology is a linguistic typology that classifies languages of the world as stress-timed or syllable-timed or some mix of the two. English is a clear example of a stress-timed language. Whereas most descriptions of strong-stress meter focus on the counting of stresses, the present study focuses on the patterns of unstressed syllables between the stresses (possibly at isochronous intervals). The implications of this analysis suggest a new typology in which certain forms of English verse follow strict grammatical stress (mainly Old and Middle English, but for reasons different from “strong-stress” expectations) and other forms are shaped by a compromise of grammatical stress and the metrical template. Within this later group, iambic pentameter contrasts with trochaic, anapestic, and dipodic meters in lending itself more readily to modulation. Some of this modulation comes from an easy incorporation into iambic pentameter of elements associated with Old and Middle English meters.