|Abstract:||This paper presents a case study of external sandhi in Spanish that bears directly upon the status of gestural representations and constraints in the synchronic grammar. Spanish has a contrast between a tap and trill between vocoids within the morpheme, which is neutralized in coda position. In the northern Peninsular Spanish varieties spoken in the Cantabrian province around Los Montes de Pas and Tudanca, infinitival -r is lost before a consonant-initial clitic pronoun or determiner but surfaces as a tap or trill in other coda environments, depending on the dialect (Penny 1969, 1978). While tap + consonant clusters exhibit an intrusive vowel between the two consonants, other consonants appearing in first position fail to trigger vowel intrusion. The proposed analysis draws upon recent developments in gestural Optimality Theory (Davidson 2003, Gafos 2002, N. Hall 2003), as well as Padgett's (2003a,b,c) version of Dispersion Theory (Flemming 1995). Conflicting gestural constraints generate different patterns of temporal coordination in consonantal sequences. Minimal overlap produces vowel intrusion in tap + consonant clusters, partial overlap favors unreleased other consonant clusters, and complete overlap yields deletion of infinitival -r in the appropriate prosodic contexts. The central claim is that the phonology must incorporate phonetically detailed gestural representations in addition to segmental and prosodic structure. In Dispersion Theory, systemic markedness constraints regulate the perceptual distinctiveness of contrasts, making it possible to incorporate phonetic detail without overgenerating contrasts.