This paper reports an acoustic and articulatory study of labio-palatalization in Twi Akan (West African). Labio-palatalization is rare cross-linguistically, as would be predicted from theories of vowel dispersion, since palatalization and labialization have opposite effects on second formant frequency. Labio-palatalization in Twi, however, is the ongoing result of a convergence of contrastive consonant rounding and vowel-induced palatalization which have been functionally combined in certain segments. Preliminary palatographic data indicate that rounded coronal consonants have more posterior coronal constrictions. Present acoustic analyses show rounded consonants to be marked by a lowering of F3. Combining coronal retraction and rounding, thus has two effects. (1) It produces a stable region of low F3, as indicated by nomograms in Wood (1986). (2) It increases front cavity length, resulting in a lower and more compact spectrum of consonantal frication noise. Thus 1) examining the role of uncommon contrasts in a phonemic system can shed light on posited mechanisms for language change, and 2) rounding may serve different roles in different language systems, to lower both front and back-cavity resonances, or a more specific role of lowering front-cavity resonances which shape consonantal noise.