Cellists' sound quality is shaped by their primary postural behavior.

During the last 20 years, the role of musicians' body movements has emerged as a central question in instrument practice: Why do musicians make so many postural movements, for instance, with their torsos and heads, while playing musical instruments? The musical significance of such ancillary gestures is still an enigma and therefore remains a major pedagogical challenge, since one does not know if these movements should be considered essential embodied skills that improve musical expressivity. Although previous studies established clear connections between musicians' body movements and musical structures (particularly for clarinet, piano or violin performances), no evidence of direct relationships between body movements and the quality of the produced timbre has ever been found. In this study, focusing on the area of bowed-string instruments, we address the problem by showing that cellists use a set of primary postural directions to develop fluid kinematic bow features (velocity, acceleration) that prevent the production of poor quality (i.e., harsh, shrill, whistling) sounds. By comparing the body-related angles between normal and posturally constrained playing situations, our results reveal that the chest rotation and vertical inclination made by cellists act as coordinative support for the kinematics of the bowing gesture. These findings support the experimental works of Alexander, especially those that showed the role of head movements with respect to the upper torso (the so-called primary control) in ensuring the smooth transmission of fine motor control in musicians all the way to the produced sound. More generally, our research highlights the importance of focusing on this fundamental postural sense to improve the quality of human activities across different domains (music, dance, sports, rehabilitation, working positions, etc.).

Exploring the perceived harshness of cello sounds by morphing and synthesis techniques.

Cello bowing requires a very fine control of the musicians' gestures to ensure the quality of the perceived sound. When the interaction between the bow hair and the string is optimal, the sound is perceived as broad and round. On the other hand, when the gestural control becomes more approximate, the sound quality deteriorates and often becomes harsh, shrill, and quavering. In this study, such a timbre degradation, often described by French cellists as harshness (décharnement), is investigated from both signal and perceptual perspectives. Harsh sounds were obtained from experienced cellists subjected to a postural constraint. A signal approach based on Gabor masks enabled us to capture the main dissimilarities between round and harsh sounds. Two complementary methods perceptually validated these signal features: First, a predictive regression model of the perceived harshness was built from sound continua obtained by a morphing technique. Next, the signal structures identified by the model were validated within a perceptual timbre space, obtained by multidimensional scaling analysis on pairs of synthesized stimuli controlled in harshness. The results revealed that the perceived harshness was due to a combination between a more chaotic harmonic behavior, a formantic emergence, and a weaker attack slope.