Voice quality differences and the origin of diphthongs

Introduction. The literature documents a widely-noted correlation between three clusters of features widely-distributed in Southeast Asian languages: a so-called tense register (associated with several distinct voice quality or phonation types (specifically, with creaky, tense, and sometimes harsh voice)), a modal register, which is unmarked, and a breathy-voiced register (associated with breathy voice). See Figure 1 for the three bundles of co-occurring features.