The effects of contextual tonal variation on Cantonese tone merging

Previous studies on Cantonese tone merging have examined monosyllabic materials so far, yet disyllabic words are common in daily conversation. Sound change often originates from a pool of synchronic variations, and coarticulation from neighbouring units is a common source. The current study examined how tonal coarticulation in disyllabic words contributes to Cantonese tone merging by examining both monosyllabic and disyllabic data from 17 merging speakers and 2 reference speakers. Materials with well-controlled tonal context for the target tones appearing as the first and the second syllables in disyllabic words were used. Results showed that tonal coarticulation and tone merging coexist, with carryover coarticulation in extreme tonal contexts being the most vulnerable condition for change. Large amounts of individual variation were observed, both in terms of cross- and within-speaker variations which could blur the difference between merging and non-merging speakers. The disyllabic data reveal both the independence and interaction of coarticulation and sound change, and allow us to consider various factors in sound change from a wider perspective at the suprasegmental level.