A musical-tone signal forming apparatus is provided for an electronic musical instrument. The apparatus comprises a musical-tone wave form setting circuit in which at least one cycle of a musical-tone wave form is repeatedly subjected to sampling at n points and the amplitude at each sampling point is compared with the amplitude at the preceeding sampling point. An increase, equal or decrease signal is generated in the form of a digital signal to indicate the relationship determined. An envelope setting circuit is provided in which an envelope of a desired musical-tone is subjected to sampling at m point and the analog amount at each sampling point is generated sequentially as a digital signal corresponding thereto. A pulse generating circuit whereby a pulse signal having a number corresponding to the digital signal value produced by the envelope setting circuit is repeatedly generated is employed. Also employed is a distribution circuit including addition and subtraction output terminals in which the output signals of the pulse generating circuit are distributed either to the addition output terminal or the subtraction output terminal according to the digital signals produced by the musical-tone wave form setting circuit. There is also used an up-down counter in which output signals of the addition output signal and the subtraction output terminal are respectively added or subtracted. A D-A converter is provided in which digital signals generated by the up-down counter are converted into analog signals.