The preservation of proto-Japanese tone class 2.5 in the Izumo region explained

Abstract

In 1981, Okumura Mitsuo reported that the dialect of Izumo Taisha in western Japan had preserved remnants of the separate tone class 2.5, which until then had only been found in dialects in central Japan. His discovery proved that this tone class had formed part of proto-Japanese, but the phonetic realization in Izumo and in central Japan was totally different. The article offers a reconstruction of the proto-system of the Izumo region, as well as an explanation of how class 2.5 came to be (partly) preserved in Izumo. It is argued that this was through a series of rightward shifts of the /H/ tone. These shifts radiated out from the northwestern part of the region. In the period, when the shifts were active, a contour tone on the second syllable of class 2.5 blocked rightward /H/ tone shift in this class. In this way, the contour tone, although later lost, left a trace in the modern dialects.