I argue that, contrary to some recent proposals, a given phonological form may be organised into at most one array of metrical structure at a time. The bulk of the paper is dedicated to a case study of Huariapano, a language that has been claimed to motivate multiple, coexisting but autonomous, layers of metrical parsing. I show that this conclusion is premature: both stress and segmental patterning in Huariapano can be modelled within a single system of constituency, once context-dependent variation in foot form is taken into account. This reanalysis also draws on the idea that foot-initial syllables may be targeted by augmentation or fortition processes even when unstressed. Independent evidence for foot-initial strengthening is furnished by segmental phonotactics in a range of other languages.