Similar phonetic and phonological processes often exist in predictable synchronic relationships across languages: when a process is phonologized, its phonetic predecessor is suppressed to resolve conflicting demands on the relevant set of acoustic cues (Cohn, 1990; Francis, Ciocca, Wong, & Chan, 2006). In the case of vowel harmony and vowel-to-vowel (VV) coarticulation, the diachronic origins of harmony in VV coarticulation are well-supported (Ohala, 1994), but their synchronic relationship is not fully understood. This dissertation investigates coarticulatory directionality in Spanish, Tatar, and Hungarian in order to better understand how stress and vowel harmony impact language-specific directional preferences in VV coarticulation. In the Spanish study, the strongest VV coarticulation occurred in unstressed vowels, while stressed vowels inhibited coarticulatory magnitude. In Tatar, the dominant direction of VV coarticulation was anticipatory, and tentative initial evidence emerged that Tatar harmony may be undergoing reanalysis with regard to a marginalized lexical subset of orthographically disharmonic items. Finally, in Hungarian, results were mixed; both anticipatory and carryover VV coarticulation predominated under different conditions. Results point to a limited impact of stress on VV coarticulatory direction, with no consistent cross-linguistic relationship between the directions of vowel harmony and VV coarticulation.