This article presents the preliminary results from an exper- iment investigating the influence of cellists’ ancillary gestures on their musical expressivity. Seven professional cellists were asked to play a score while their movements were recorded by a force platform (on which they were seated) and a 3D motion capture system for joint kinematics. Spe- cific torso and head contributions to their global postural displacements were analyzed through the use of 4 playing conditions: (a) a normal con- dition without any constraints, (b) a mentally static condition where the cellists were asked to keep their posture as static as possible, (c) a phys- ically semi-constrained condition where the cellists’ torso was attached to the back of a chair by a safety race harness, and (d) a physically fully constrained condition where the cellists wore a neck collar in addition to the race harness to limit their head movements. We here investigate the influence of these constraints on global postural features computed from the force platform data, and on fundamental acoustical features linked to musical expressivity for one cellist. The first results reveal that the cel- lists’ immobilization conditions give rise to different postural adaptation strategies depending on the torso-head coupling, and alter significantly the expressive intentions through changes in spectro-temporal features and rhythmical variations of the produced sounds.