Electroacoustic sustainer for musical instruments

An electroacoustic-type sustainer is provided for prolonging the vibrations of strings of a stringed musical instrument. The instrument has at least one magnetic pickup means responsive to the vibrations of the strings. The instrument pickup produces an output signal in response to the vibrations of the instrument strings. The sustainer comprises a string driver transducer capable of inducing vibrations in the strings, a sustainer amplifier having an input which accepts the pickup output signal, a control circuit to modify the pickup output signal, and an amplifier circuit which amplifies the pickup output signal to produce a drive signal. The sustainer amplifier has an output, from which the drive signal transfers sufficient energy to the string driver transducer to sustain the vibrations of the strings. The transducer has magnetic symmetry, providing less magnetic radiation than previous designs. The transducer is simple in construction. The transducer has an improved mounting design, for attachment to a musical instrument, and which efficiently coupled transducer vibrations to the instrument body. The transducer has an improved cord routing system. The sustainer has an improved automatic harmonic mode control for changing the harmonic vibration mode of the sustained string vibrations.