In this study, a reconstruction is offered for the phonetic evolution of rhymes from Old Tibetan to modern-day Amdo Tibetan dialects. The relevant sound changes are proposed, along with their relative chronological precedence and the dating of some specific changes. Most interestingly, although Amdo Tibetan, identically to its ancestor Old Tibetan, does not have phonemic length, this study shows that Amdo Tibetan derives from an intermediate stage which, like many other Tibetan dialects, does make the distinction.
