Yuhuan Wu tone sandhi and tone contrast maintenance

Yuhuan Wu Chinese deletes non-final lexical tones within a small post-lexical tone domain, except HL if its syllable begins with a sonorant consonant. The explanation of this phonological specification lies in the number of tone contrasts in the location concerned (H, L, HL, ML and LH), which is higher than in syllables with a voiceless obstruent or zero onset (H, HL, LH) or in syllables beginning with a voiced obstruent (L, ML, LH). The interpretation as contrast maintenance is supported by features of two phonetic implementation rules which enhance tone contrasts. One enhances the incompleteness of the neutralization of tones in pre-final position, while the other enhances the ML-HL contrast in phrase final position.