Design and implementation of a real-time digital resonator for the electric cello

Electric stringed instruments such as the electric violin and the electric cello have recently become quite popular. Unlike ordinary stringed instrume nts, the bodies of most of these electric stringed instruments have no acou stical function at all; the instruments produce sound without resonance fro m the instrument body. As illustrated in Figure 1, waveforms of the lowest cello pitch (C2) played on an acoustic cello and an electric cello are quit e different. The two signals shown were taken from the same cellist who use d the same playing style (simple bowing); the strings of the two cellos wer e also identical. A MIDI controller is commonly used to improve the quality of the sound prod uced by these electric stringed instruments. However, MIDI is not designed to process sounds per se, but rather to simply provide a common interface t o computers and synthesizers. Furthermore, most synthesis techniques do not retain much of the player's original performance style or nuance. Thus, re cent research has investigated new paradigms of performer-instrument-synthe sis interaction. Paradise and Gershenfeld (1997) usedd sensors to measure p layers' expressions, and sent the sensor Outputs to a computer network for improving the synthesized sounds of a "hypercello." Mathews and Kohut (1973 ) proposed using an analog filter bank to produce resonances for the electr ic violin. However, the frequency response of the filter bank is difficult to tune for all pitches, making production of a natural violin sound diffic ult. To remedy this problem, we consider different frequency responses for different pitches in our system.