The component tone signal commonly shared by a plurality of keys does not turn to a release signal if one of the keys is released to stop a tone and also while tones of other keys are sustained; the on-data of each key of the keyboard is multiplied in multiplier by the amplitude data set by the draw-bar circuit with the multipliers, added with adder and sent to the sound source circuit; the sine waves of the same waveform and different cycles are generated according to the amplitude data, are synthesized with envelopes from envelope generator, and the added with adder; this envelope generator is disposed at every sound source circuit, that is, every one of the common component tone signals; the component tone signal/sine wave commonly shared by a plurality of keys does not turn to direct to a release state if one of the keys is operated to stop a tone, and also directs not to turn to a release state but to maintain a sustain state while tones of the other keys are sustained.