There has been accumulating evidence in recent years that certain F0 events are consistently aligned with segmental events such as the syllable boundary. The mechanisms for the observed alignment patterns, however, are still being closely investigated. In this paper I argue that to understand the observed tonal alignment patterns, it is imperative to first understand the role of articulatory constraints in shaping the F0 contours in speech. In particular, the maximum speed of pitch change limits how fast F0 movements can be produced; and the coordination of laryngeal and supralaryngeal movements limits how syllables and tones can be aligned to each other. From a different perspective, these constraints mean that the degrees of freedom speakers have are probably less than previously thought. This may actually make our understanding of the speech signal somewhat easier than before. I will demonstrate this with a theoretical model of F0 production that is based on the new understanding of the articulatory constraints. Though conceptually simple, the model seems to be able to account for a number of phonetic patterns that have been observed in speech. Finally, I will briefly discuss the implications of the new insights on our understanding of tonal perception in speech.