Abstract: In this talk, I argue that a subset of cross-linguistically common lenition processes such as spirantization, intervocalic voicing, and flapping take place in a component of grammar that governs the fine-grained temporal dynamics of speech sounds and their interaction with prosodic structure, and *not* in a component of grammar that changes phonological features. I review cross-linguistic evidence that these lenition patterns are different from other processes sometimes referred to as ‘lenition’; that they do not manipulate phonological features; that they lie on a broader continuum of prosodically-driven phonetic variation; and that they operate primarily through subphonemic adjustments to duration and the temporal separation between prosodic units. With data from Campidanese Sardinian, I illustrate a schematic approach to modeling lenition as a language-specific property of phonetic implementation, operating on prosodic structure and the output of narrow phonology.