Sound enrichment of the cristal Baschet by the whiskers

The cristal Baschet is a musical instrument created during the 50’s by Bernard and Francois Baschet. It is composed of a large number of glass rods arranged in a chromatic scale. Frictional interaction between wet fingers and glass rods triggers self-sustaining vibrations of the resonator, assembly of metal parts and glass rod, which are transmitted to acoustic radiators. The instrument can be equipped with auxiliary elements to modify its timbre. In particular, long thin metal rods called whiskers are commonly added. They act as additional resonators that induce sound enrichment by emphasizing certain higher harmonics. As the manufacturing process of this instrument relies on empirical knowledge, the way whiskers should be tuned to achieve the desired effect is not well known. In this study, modal experimental analysis and numerical modeling are used to understand the dynamic behavior of whiskers and their interaction with the rest of the instrument. First, the simplified structure which is composed of one resonator and one whisker is studied. Experimental measurements are compared with time-domain simulations to gain insight into the role of whiskers and propose tuning guidelines. It is demonstrated that a slow oscillation of the whisker induces a modulation of some specific modes for which the longitudinal and flexural motions are strongly coupled. Such modulation of high order spectral components of the cristal’s sound induces an unusual and characteristic timbre.