Abstract
The biwa, a family of Japanese lutes played with plectrum, produces a tone of peculiar timbre called the sawari tone caused by dynamic contact of the vibrating string with a small instrumental device called the sawari. This paper presents a physical model consisting of a linear string-resonator system to which the sawari is added so as to work as a unilateral constraint to the vibrating string. Included also is a stick-slip mechanism of plucking to simulate the so-called touch noise that exists as a precursor in the biwa tones (and in the tones of some other string instruments played with plectrum.) A numerical simulation was conducted in search for the condition that produces sawari-like tones as characterized by a unique temporal profile of the total amplitude and its constituting partials. The result showed that the system produces simulated tones that resemble a genuine sawari tone, called the reference tone, when the size of sawari is about the same as that of the instrument on which the reference tone was produced, under the condition that the model string is plucked at a point belonging to a specific portion off the bridge.
