Signal-selecting system for a keyboard type electronic musical instrument

Claim 1

A signal selecting system for a keyboard type electronic musical instrument, comprising: a plurality of keyswitches actuated by a plurality of corresponding keyboard keys, respectively, and which are in a range of more than two octaves and being grouped in a plurality of octave groups the number of which is equal to the number of octaves; preference circuit means including said octave groups of keyswitches coupled in said preference circuit means for selecting the extreme keyswitch from among keyswitches closed simultaneously in each of said octave groups of keyswitches; 12 memory means corresponding to the 12 notes of one octave and coupled through said preference circuit means to corresponding keyswitches for the same notes in the respective groups; 12 tone signal sources for generating tone signals corresponding to said 12 notes of one octave; 12 signal switching means connected between said 12 memory means and the corresponding 12 tone signal sources for switching on a tone signal source upon the operation of the corresponding memory means, said preference circuit means coupled to said memory means for switching on and setting the memory corresponding to the keyswitch which is closed; frequency divider means having a plurality of frequency dividers connected to the outputs of said 12 signal switching means, the frequency dividers being connected in series, said frequency dividers dividing the frequency of the tone signal applied thereto by a factor of two; a power supply terminal; an octave-selecting means comprising a first detecting means coupled to said preference circuit means for automatically selecting the octave group of keyswitches for the extreme octave from among the octave groups containing the extreme keyswitch among keyswitches closed simultaneously in the whole range of said plurality of keyswitches and including a further memory means connected to said first detecting means for memorizing which of said extreme octave group of keyswitches is operable; said octave-selecting means further comprising means connected between said further memory means and said frequency divider means for determining the number of frequency dividers practically operable in said frequency divider means so that said signal selecting system produces one tone signal corresponding to the extreme keyswitch among keyswitches closed simultaneously among all of said keyswitches through the corresponding one of said 12 signal switching means and said frequency divider means from the corresponding one of said 12 tone signal sources; and a second detecting means coupled to said power supply terminal, said first detecting means and said 12 memory means for detecting a moment when the state of closed keyswitches is changed so as to reset the memory state of said 12 memory means and said further memory means.