It has been heretofore conventional that the forming of a musical-tone signal for an electronic musical instrument is effected by forming a musical-tone signal waveform and passing the same through an envelope circuit to obtain a musical-tone signal having a specific envelope.
This envelope circuit requires a condenser and is defective in that the condenser may be rather large in size. As a result of the necessity of limiting the capacity for that reason, available envelopes are limited to those within a certain range and many envelopes which characterize various natural musical instruments or which have to be specially created cannot be formed as occasion demands.