Assessing the Effects of a Primary Control Impairment on the Cellists’ Bowing Gesture Inducing Harsh Sounds

How do cellists' postural movements influence timbre quality during instrumental performance? If this question seems complex at a first glance partly due to specific motor synergies for each musician, some principles of postural organization are believed to remain invariant while executing bowing gestures. In this paper, we reveal some of these common principles by investigating the effects of postural constraints on the mechanical behavior of the cellists' right arm, and consequently on the resulting bow velocity likely to cause timbre degradation, referred to as harshness (“
décharnement
” in French) by cellists. The kinematical data corresponding to the execution of a single note are collected through a motion capture system, and analyzed between two postural conditions of expressive playing: A normal one and a constrained one limiting chest and head displacements involved in the cellists'
primary control
. The comparison of relevant joint displacements and rotations between the two postural situations highlight the lack of coordination between spine torsion and shoulder opening as a main factor responsible for a tighter right arm gesture, potentially leading to a drop in bow velocity and consequently the production of harsh sounds.