Abstract: Electrical circuitry for varying the relative distinctiveness between the lead and rhythm audio signals produced by an electrical guitar, or the like, according to the strength with which the musician picks the guitar strings. The rhythm signal is compressed in response to how hard the player strums or picks the guitar, while the lead signal is expanded as a direct function of rhythm signal compression. An electrical signal is generated from the rhythm signal for controlling the extent of compression and expansion of the audio signals.

Abstract: A keyboard for a monophonic musical instrument has a plurality of touch sensitive keys which function as variable capacitors, the capacitance depending on the force applied to the keys. The variable capacitance is detected and used to produce a variable control voltage which is used to execute one or several of various control functions, such as controlling the volume of the sound produced by The instrument, controlling the cutoff frequency of a low pass filter in the output system of the instrument, controlling the amount of vibrato or other periodic modulation introduced into the sounds produced by the instrument, controlling the frequency of the vibrato or other periodic modulation, or controlling the amount of "bend" in the pitch of a sound produced by the instrument, i.e. shifting the pitch slightly from its nominal value. The variable capacitors employ a conductive elastomer which is deformed in response to the force applied to the keys.

Abstract: An electronic music synthesizer is disclosed in which the sound producing chain includes a voltage-controlled oscillator, band-pass filter, low-pass filter, and amplifier in which selected control currents are supplied to low impedance points within the synthesizer circuit from a resistor matrix. The synthesizer produces sounds approximating different acoustic musical instruments or having different tonal qualities by the application of a predetermined voltage to one of fifteen input columns of the resistor matrix with selected other columns being grounded. The currents provided by the resistor matrix in combination with other externally generated currents control the center frequency and bandwidth of the band-pass filter, the cutoff frequency of the low-pass filter, the gain of the voltage-controlled amplifier, the time constants of transient contour currents used to control the filters and amplifier, and the waveform produced by the voltage-controlled oscillator.

Abstract: A sound effect circuit with a phase shifter producing a signal shifted in phase with respect to an input signal, a combining circuit for arithmetically combining the input and phase shifted signals to produce an output signal, an oscillator for periodically modulating a characteristic frequency of the phase shifter and a modulation control circuit. The modulation control circuit causes the modulation rate to gradually increase when modulation is manually switched on and to gradually decrease when modulation is switched off. The modulation control also causes the characteristic frequency to vary inversely with the modulation rate.

Abstract: A distortion sound effects circuit producing an output signal corresponding to an input signal but containing one of four selected types of distortion. A compressor which includes a voltage-controlled amplifier first compresses the audio input signal within preselected limits, and the distortion operations are performed on the compressed audio signal to advantageously render the subsequent distortion operations insensitive to gross amplitude fluctuations of the input signal. The compressor includes means for full-wave rectifying the compressed audio signal. The full-wave rectified signal is provided as a distorted output signal containing hard-even distortion of the type commonly achieved by severely, asymmetrically clipping a signal. A distortion circuit includes single voltage controlled square-low amplifier to which the compressed audio signal is applied performs the other three types of distortion.