When tone prevents vowels from gliding (and when it does not)

Since the mid-1970’s it is well known that tone in many languages behaves independently from its tone bearing unit, and conspiracy arguments lead to consider tone as a distinct item. However, tone is commonly sensitive to some specific segments, and is sometimes involved in a specific relationship with its bearing units. Nevertheless, little attention has been paid so far to the fact that, in some languages, tone has a direct effect on the vowel to which it is associated. In this article, it is demonstrated that a tone may prevent the deletion or the gliding of a vowel resulting from hiatus situations. This assertion is supported by a detailed analysis of similar phenomena in the Bantu language Shingazidja. In a first attempt of an OT analysis, it is proposed that the absence of gliding may result from the high ranking of a constraint V´-μ,, which says that a tone bearing unit has to be moraic.