Patent GB-1173954-A (GB)
Title: Improvements in or relating to Electronic Musical Instruments
Inventor: OMURA MASUO
IPC: G10H1/08
Filed: 1967-02-13
Abstract: 1,173,954. Electronic organs. MATSUSHITA ELECTRIC INDUSTRIAL CO. Ltd. 13 Feb., 1967, No. 6751/67. Heading G5J. In an electronic organ the tones produced by the tone generator system are combined in such a way that their frequencies lie in a 2<SP>n</SP> progression extending over a range of at least three octaves, n being an integer greater than unity, to produce multi-pitch signals which can be selected as required by switches operated by keys of a keyboard for application to a sound reproducing system. Tones produced by a fixed frequency oscillator such as 9 are fed into a chain of frequency dividers 12, 13 &c., each of which divides the frequency of its input tone by two and feeds the divided frequency tone to the next divider. There is an output from each divider stage and the tones are combined into many various groups having required amplitude relations by mixing resistors 37, 38 &c., and fed to a key-switch 31. These tone signals are switched by tone control switches 67, 68 &c., and fed to tone forming circuits 72, 73 &c., and thence to the acoustic system to produce the audible sound. The high frequency components in the multi-pitch signal can be intensified by connecting a shunt capacitor across one of the resistors in the mixing network as in Fig. 34 (not shown). In another embodiment the tones can also be mixed by a circuit as in Fig. 22 (not shown) where two tone signals are employed, one being a single pitch signal fed via a resistor (161) and the other being a multi-pitch signal fed via resistors (151, 152, 153, 154). Both tone signals are connected separately to the key-switch and are fed to the tone forming circuits (4). In a further described embodiment, Fig. 26 (not shown), three tone signals are switched simultaneously by each key, when any one or combination can be used by employing a tone forming system with tone forming circuits (241-245) switched in circuit by switches (246-250). In another embodiment, Fig. 27 (not shown), a tone obtained from one frequency divider chain is mixed with tones from a second frequency divider chain, via a low pass filter (264) in place of one of the tones of the second frequency divider chain to introduce a note in musical fifth relation to the tone it replaces. The lowpass filter prevents the generation of unfavourable beat notes. In a more complicated embodiment, Fig. 28 (not shown) components from two frequency divider chains are mixed via low pass filters (298, 299) with the tones of a third frequency divider chain in place of two of the tones of that third chain to introduce tones in musical fifth and musical third relationship to the one and the other of the absent tones respectively. In a further embodiment, Fig. 31 (not shown) the multi-tone signal supplied to certain key-switches (318) is composed of components derived partly from one frequency divider chain and partly from a device (343) developing a difference tone signal from a mixture of two tone signals, one from one frequency divider chain and one from another. The device (343) appears in detail in Figs. 32 or 33 (not shown) and comprises a diode in parallel with a resistance across the input followed by a low pass filter.