This book presents a detailed and enlightening examination of the effects of duration and sonority on the pattens of positional restriction of contour tones. Through a typological survey and analysis of 187 genetically diverse languages the author challenges the theoretical standpoint from which the problem has been traditionally addressed and adds to the growing amount of data which places the dichotomy between phonology and phonetics into question. The results of this rigorous investigation are, the author argues, inexpressible in traditional phonology and requires an innovative collapsing of the older model's operative distinction. This new theoretical model allows the author to provide a hitherto unavailable accounting of contour tones, but also represents a major theoretical contribution in its own right.