Performative control of voice is the process of real-time speech synthesis or modification by the means of hands or feet gestures. Vokinesis, a system for real-time rhythm and pitch modification and control of singing is presented. Pitch and vocal effort are controlled by a stylus on a graphic tablet. The concept of Syllabic Control Points (SCP) is introduced for timing and rhythm control. A chain of phonetic syllables have two types of temporal phases : the steady phases, which correspond to the vocalic nuclei, and the transient phases, which correspond to the attacks and/or codas. Thus, syllabic rhythm control methods need transient and steady phases control points, corresponding to the ancient concept of the arsis and thesis is prosodic theory. SCP allow for accurate control of articulation, using hand or feet. In the \emph{Tap mode}, SCP are triggered by pressing and releasing a control button. In the \emph{Fader mode}, continuous variation of the SCP sequencing rate is controlled with expression pedals. Vokinesis has been tested successfully in musical performances, using both syllabic rhythm control modes. This system opens new musical possibilities, and can be extended to other types of sounds beyond voice.