GB1185888A - A Method and a Device for Generating a Tone Scale in Musical Instruments - Google Patents

Abstract

1,185,888. Tuning musical instruments. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 27 June, 1967 [30 June, 1966], No. 29525/67. Heading G5J. A device for generating a tempered twelvetone scale in electronic musical instruments comprises twelve oscillators, each generating a tone in the octave, the frequencies of three tones satisfying the equations f n-2 - f n-3 = f n /20 = f n-12 /10, in which n is the ordinal number of the tone in the scale, one oscillator frequency being adjusted independently and the other frequencies being controlled by signals derived from two of the other oscillators. As shown in Fig. 1, each oscillator consists of a Schmitt trigger ST, with feedback via R 1 , R 2 , R 3 , C 1 , controlling the period of the rectangular output, and a bi-stable flip-flop FF 1 , producing the basic frequency f n which is divided by two at each of the flip-flops FF 2 , FF 3 , and by five by the divider Sc 5 , to give a tone of frequency f n /20. Output signals from B n and C n of FF 2 , FF 3 respectively generate tones of frequencies f n /2, f n /4 in adjacent lower octaves. The frequency fn/20 is compared with frequencies f n-3 , f n-2 in an AND-gate consisting of diodes D 1 , D 2 , D 3 , D 4 , the current produced by this coincidence unit being integrated in a capacitor C 2 , which delivers a control voltage to an output terminal D n , this control voltage being used to regulate one of the input frequencies to the coincidence unit. The basic frequency setting of each oscillator may be changed by a stabilized voltage V +, and an individually set potentiometer P in each oscillator compensates for variations in the effect of V + . The coincidence unit may be replaced by a phase-sensitive detector. The oscillators may be crystal controlled, and the synchronization method can be applied to a mechanical system. Frequency multiplication may be used instead of frequency division.