GB1335953A - Dc keyed synthesis organ - Google Patents

Abstract

1335953 Electrophonic musical instruments HAMMOND CORP 7 April 1972 [19 April 1971] 16219/72 Heading G5J In a keying system for simultaneously keying the desired group of harmonic and fundamental frequencies for a note produced in a synthesis type electric organ, a substrate block 10 corresponding to one of the selectable notes on the keyboard, is divided into nine identical sections marked SF, S3, F, 2, 3, 4, 5, 6 and 8 which each contain a pair of MOSFET transistors 82, 84, which switch, on actuation of playing key 92, into the output section 106 via sinusoidal signal filters 102, the square wave signals 34, 36, 20, 22, 24, 26, 28, 30, 32 respectively, which are applied at the gate of each respective transistor 82, and which correspond to the subfundamental, subthird, fundamental, second harmonic, third harmonic, fourth harmonic, fifth harmonic, sixth harmonic and eighth harmonic frequencies of the note selected by actuating key 92, which connects a - 25 V gating voltage via an envelope shaping circuit comprising, e.g. components 96, 98, 100, to the gates of MOSFET's 84. The relative amplitudes of the harmonics so filtered and mixed can be adjusted individually, to vary the tone colour of the note produced by means of slides at 60. Each slide 62 is connected to the input of each corresponding transistor 82 and applies a variable voltage thereto obtained from voltage supply 40 via tapped resistor 42, thus varying the gain of the transistor and hence the amplitude of the square wave signal controlled by each transistor 84. In a further embodiment, transistors 82 and 84 are interchanged.