Physically Informed Sonic Modeling (PhISM): Synthesis of Percussive Sounds

Abstract

Percussion instruments represent a broader spectrum of physical configurations than any other instrument family. Orchestration books, acoustics books, and taxonomies of instruments often lump some instruments into the percussion family not because of what they are, but just because they don't fit into the other instrument families. One loose characterization might state that percussion instruments exhibit exponentially decaying modes that are excited by striking. This results in the piano's being categorized as a percussion instrument, but this definition does nothing to address the many percussion instruments that can be shaken or rubbed continuously, nor those that don't exhibit any clear modal behaviors. The physical components of percussion instruments include bars, plates, membranes, cavity and tube resonators, and nonlinearities of countless types, all coupled to each other in varieties of ways. Because of this variety, there exist no common model features that allow the percussion family to be captured with simple changes in model topology, or with variations of the parameters of a meta-model. By grouping the percussion family into subfamilies, some similarities can be exploited, but there are still large varieties of configurations and excitation means. Another important aspect of percussion instruments is their relationship to everyday (nonmusical) sounds. Walking, preparing food, working with metal and wood tools, riding a bicycle, etc., all create sounds that are closely related to members of the percussion family. The expressive nature of percussion lies in the ability to excite objects, with various objects, and in numerous ways. Sampling synthesis of percussion instruments based on digital recordings lacks the means for manipulating parameters in musical a d physically meaningful ways. There has been ome work on more-efficient physical modeling of embranes (Van Duyne and Smith 1993), and modeling of nonlinearities in percussion instruments (Van Duyne, Pierce, and Smith 1994). However, direct real-time synthesis of many percussion instruments by physical modeling is likely to remain beyond practical computing means for some time to come. Even if computing power were sufficient to make exhaustive physical modeling of percussion instruments economical, the physical mechanisms of many such systems are still not completely understood.