This paper deals with the study of tone in languages that additionally have a phonological contrastive of quantity, such as vowel length or stress. In such complex word-prosodic systems, tone and the quantity contrast(s) can be fully independent of one another, or they may interact. Both of these configurations are illustrated in this paper, and the phonetic pressures underlying the development of interactions are laid out. The paper pays particular attention to the challenge of investigating complex word-prosodic systems. Central to the approach advocated here is the combination of qualitative fieldwork data collection methods with instrumental analysis.