Abstract: An electronic audio signal processor circuit particularly suited for electrical instruments as an electric bass guitar for providng controlled distortion and tone alteration. The circuitry includes a compressor circuit at the input operated in conjunction with a detector which in accordance with the invention is an RMS detector. Also, at the input circuitry is a distortion switch which controls the type of distortion that is generated. This distortion switch is used in conjunction with a distortion amplifier, the output of which couples to a resistive sensing network. The network feeds the audio signals to a low EQ circuit, a mid EQ circuit and a high EQ circuit. Associated with the high EQ circuit is a clipper switch and at the output of the EQ circuitry is an EQ switch for providing a preferred predetermined frequency response wave forms. A high frequency compressor and associated switch is also associated with the EQ switch.