String Stretching, Frequency Modulation, and Banjo Clang

Abstract

The banjo's floating bridge, string break angle, and flexible drumhead all contribute to substantial audio range frequency modulation. From the world of electronic music synthesis, it is known that modulating higher frequency sounds with lower acoustic frequencies leads to metallic and bell-like tone. The mechanics of the banjo does just that quite naturally, modulating fundamentals and harmonics with the motion of the bridge. In technical terms, with a floating bridge, string stretching is first order in bridge motion, in contrast to it being second order in the vibration amplitude of the strings.

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