Toward a generalized friction controller: from the bowed string to unusual musical instruments. Stefania Serafin Medialogy Aalborg University Denmark sts@cs.aue.auc.dk Diana Young MIT Media Lab Cambridge, MA diana@media.mit.edu ABSTRACT We present case studies of unusual instruments that share the same excitation mechanism as that of the bowed string. The musical saw, Tibetan singing bow, glass harmonica, and bowed cymbal all produce sound by rubbing a hard object on the surface of the instrument. For each, we discuss the design of its physical model and present a means for ex- pressively controlling it. Finally, we propose a new kind of generalized friction controller to be used in all these exam- ples. 1. INTRODUCTION Playability of physical models is an area of increasing in- terest in recent years. As the synthesis techniques have be- come suitably refined to compare favorably with their real instrument counterparts, access to the many musical possi- bilities they offer has remained somewhat limited from the standpoint of the performer. That is, though they provide ample material for use in new compositions [8], and even in- spire the creation of new compositional techniques and no- tations [1], they are still generally quite removed from the easy intuitive control of performers. Only when there are natural and instinctive physical ways of playing the sophis- ticated models in existence today, will these models emerge as true instruments in spite of their virtual origin. Previously, an ongoing virtual violin project was described [10, 14], in which a bowed string controller is used to explore the playability of a violin physical model. Though the violin is an example of a highly sophisticated traditional instru- ment that requires a very complicated playing technique, it relies on an excitation mechanism that is common to many instruments that may be considered unusual by comparison. This paper addresses the issues of controlling physical models of instruments that possess a friction-based excita- tion mechanism such as that found in the bow-string interac- tion and the musical possibilities such control might afford. Discussed below are the musical saw, Tibetan singing bowl, NIME 2004 Hamamatzu, Japan . glass harmonica, and bowed cymbal. We also propose a new generalized controller for friction driven instruments. This controller is able to drive all the instruments described in this paper, as well as other sonori- ties which are produced by rubbing dry surfaces. 2. TIBETAN BOWL AND GLASS HARMON- ICA 2.1 The Tibetan bowl Oral tradition dates the singing bowl back to 560-180 B.C. in Tibet. These bowls have been found in temples, monas- teries, and meditation halls throughout the world. Singing bowls are said to be made out of five to seven metals such as gold, silver, mercury, copper, iron, metal and tin, each representing a celestial body. Each of these metals is said to produce an individual sound, including partials, and to- gether these sounds produce the exceptional singing sound of the bowl. Each bowl is hand hammered round to pro- duce beautiful harmonic tones and vibrations. Today they are used in music, relaxation, meditation, and healing. Figure 1: The Tibetan singing bowl used as a starting point for the physical model. 2.2 The glass harmonica Glass harmonicas are musical instruments of two kinds. The first one, invented by Benjamin Franklin, adopts glass bowls turned by a horizontal axle so that one side of the bowl dips into a trough of water. The second one is a com- bination of wineglasses similar to the ones shown in figure Proceedings of the 2004 Conference on New Interfaces for Musical Expression (NIME04), Hamamatsu, Japan NIME04 - 108