GB1258853A - - Google Patents

Abstract

1,258,853. Electronic musical instruments. J. S. ALLEN. 5 Oct., 1970 [6 Oct., 1969], No. 47206/70. Heading G5J. An electronic musical instrument for simulating a stringed instrument such as a guitar comprises strings 17a-17f held taut by springs 19 and extending only on the table 16, the vibrations of which are picked up by piezoelectric transducers 21, 22, and columns of touch plates 26a-26f comprising wire segments 27 which actuate tone generators when touched by a finger. The columns 26a-26f, which represent the strings on the neck of a guitar, may be tuned by means of knobs 14a-14f on tuning machine resistors 32a-32f. The collective tuning, or a simulated capo, of the columns is provided by potentiometers 68, 69. On touching one of the wire segments 27 on column 26f, a virtual capacitance is formed which is coupled to a series of resistors 31f which includes a VRF voltage supply at one end, provided by rf oscillator 30. This capacitance activates oscillator 29f which oscillates at the frequency corresponding to the touched wire. Oscillations pass through isolation amplifier 35f which prevents the loading of the oscillator by subsequent circuits. Harmonic content of the oscillations is controlled by balanced modulator 41f with capacitor 42f across its input and output terminals which may be varied by potentiometer 47f. Modulators 36f and 51f are responsive to the bowing or plucking of the strings to modulate the audio frequency from oscillator 29f, modulator 36f being responsive to transducers 21, and modulator 51f being responsive to transducers 22. The respective stretching and shaping circuits 53f, 57f may be varied to alter the amount of stretching. When no segments 27 are touched, a mating pulse due to the change in input potential of rf oscillator 30 is passed to the stretching and shaping circuits. The oscillator 29f may produce a sawtooth waveform, the harmonic content of which may be controlled by a variable symmetry chopper, instead of the illustrated modulator 41f and capacitor 42f. Tremolo or vibrato effects may be obtained by utilizing a control unit coupled to resistor 33. The variation in pressure on the wire segments causes a change in the input voltage of the rf oscillator 30 and therefore the voltage on resistor 33 which causes a variation in the tuning voltage of oscillator 29f, thus obtaining a vibrato effect. Control units may alternatively be coupled to the chopper and to the stretching and shaping circuits for special effects of modulation. The oscillations may be filtered after passing through amplifier 60 using a series of # filters.