An electronic instrument for simulating the sound of a plucked string bass or other stringed instrument is described. The instrument incorporates a circuit in which the shunt resistance of a resistive capacitive phase shift oscillator is varied selectively in order to more closely simulate the sound generated by a stringed instrument, where the string is more taut when first plucked and consequently at a higher pitch than after its vibration has damped. The circuit also incorporates a switching arrangement whereby a note can be played either with a gradual decay following release of the key or with a decay while the key is depressed and a rapid cutoff when the key is released in order to permit the person utilizing the instrument to have effective control over the staccato effect.