This article aims to acquire a better knowledge of prosody disturbances in Parkinson disease via an acoustic analysis. The investigation of the patients’ vocal productions by the way of acoustic analyses should indeed allows two things. Firstly, to identify phonetic and prosodic parameters that are specific of such a pathology. Secondly, to study the effect of a pharmacological treatment (based on dopamine) on these patients’ speech production. In order to determine the effect of dopamine, oral productions of 8 parkinsonian patients of the akinetic type have been collected, in the OFF and ON states, and have then been compared to those of control subjects. The specific aim of this study is (a) to examine the ability of patients to handle the variations in fundamental frequency of their voice as well as to master the rise in frequency required by the task (i.e. production of the musical scale and intonation patterns) and (b) to measure the palliative effects that can be induced, at least partly, in the management of frequency by a treatment based on L-Dopa.