This paper presents a detailed acoustic and auditory description of the kind of complex tone sandhi found in the Northern Wu dialects of Chinese. Mean fundamental frequency, amplitude and duration values from many tokens of 1 native speaker of Zhenhai dialect are used to show how the acoustical characteristics of the 6 citation tones can be related to the 20 different forms in disyllabic lexical sandhi. Three phonetically motivated processes are demonstrated in this relationship: stress effects; paradigmatic replacement of pitch and phonation type features on the second syllable, and intrinsic effects associated with the intervocalic consonant, and phonation rate and duration of the first syllable.