In this paper, we present a study on the influence of the expressivity on the articulation degree. It is part of a project that aims to transform the expressivity of an utterance for artistic purposes, such as cinema, theater and contemporary music. An algorithm for formant frequency estimation is presented. Then a measurement of the articulation degree is proposed involving a joint statistical analysis of the vocalic triangle area and of the speech rate. The application of this measurement to an expressive French database, shows that the articulation degree depends on expressivity. Using Lindblom’s theoretical framework, we have tried to relate this articulation degree to the activation degree of a dimensional representation of emotions. Finally, speech processing is used to modify the articulation degree of a spoken or synthesized neutral utterance in order to apply a given expressivity to it.