This talk presents two research projects themed on tone development and change. The first part focuses on contemporary tonal variation, through an acoustic-phonetic case study of tones in Plastic Mandarin, a newly crystallised urban variety spoken by younger generations in Changsha, China. Drawing on fieldwork speech data and analysis using Generalised Additive Mixed Models, the study reveals how citation tones and neutral tone are realised in both Standard and Plastic Mandarin and situates the findings within the framework of new dialect formation. The second part looks to the past, exploring a possible pathway of tone emergence through a psychoacoustic experiment. This on-going big team science project aims to advance our understanding of microprosodic pitch perception in speech. Together, these studies offer new insights into the mechanisms underlying tone innovation and change in human language.