D R A W I N G
A first memory digitally stores the levels of the spectra of the fundamental wave and each harmonic up to the mth harmonic of intended tone color waves, a second memory digitally stores values XO through XN of a sinusoidal wave function at the respective points in its one cycle sampled by a sampling number N, and a third memory is for writing incoming information to be thereafter read out. Digital signals (a, b, . . . z) each representing amplitude of the respective tone color are sequentially and repetitiously produced. The levels of the spectra (fundamentals: a1b1, . . . z1; second harmonics: a2, b2 . . . z2; . . . ; mth harmonics: am, bm, . . . zm) for the respective tone color waves are sequentially read from the first memory. The amplitude signals and the level signals are respectively multiplied with each other tone color by tone color, and thereafter are added cumulatively for each of the fundamental waves and the harmonics to produce each cumulative value Hp (a X ap) + (b X bp) + . . . + (z X zp); where p . . . ,m. On the other hand, values of the sinusoidal function at the respective address points PQ mod N, where Q 1, . . . N, are read from the second memory and these read out outputs are multiplied by the respective value Hp. The products of the multiplication are added cumulatively for values H1 through Hm to obtain a signal