JPS54103339A - Electronic musical instrument - Google Patents

Abstract

PURPOSE: To automatically control the sound volume at the operating of multiple keys with a simple constitution by controlling the sound volume by the musical tone signals formed by multiplication of pitch waveform signals and time shared multiplex key touch singals corresponding to plural key touches, according to the key touch part.

CONSTITUTION: Each time when key touch is detected by a key switch scanning circuit, the time shared multiplex key touch signal TDM becomes a carry signal, by which the contents of an adder 72 are added, then the adder 72 and shift register 74 count the digital key touch number of specified bit. This count value is latched in a latch circuit 75 upon ending of the scanning and is logarithmically added in an adder 77 with the minus logarithmic weight which becomes large for the upper bit outputted by a converter 76 to become the digital time shared multiplex key touch signal of the logarithic display having been decreased as the number of key touches is larger. This signal is then applied to an adder 78 to which the waveform digital signal of the frequency being logarithmically displayed in correspondence to the touched key pitches. Hence, the sound volume of the musical tone signals formed by the multiplication of the waveform signals corresponding to the touched key pitch frequencies and the time shared multiplex key touch signals is automatically controlled.

COPYRIGHT: (C)1979,JPO&Japio