PURPOSE:To make a multiplier circuit unnecessary by providing a read-only memory circuit storing sampling data corresponding to each amplitude, a segment address counter circuit and a block address counter circuit. CONSTITUTION:The read-only memory circuit 30 stores blocks of one period, which are obtained by arranging digital sampling signals with phases the same as a steadily increasing sound waveform and its different amplitude in the increasing order of the amplitude so as to take for one block. The block address counter circuit 20 designates the block corresponding to each phase, and is jogged by the block of a sampling period. The segment address counter circuit 10 designates an address in the block corresponding to the amplitude. And the output of the block address counter circuit 20 is set to the high order side of the address, while that of the segment address counter 10 is set to the low order side of the address. Then data in the read-only memory circuit 30 is read out, whereby the sampling data on a steadily increasing sound can be read out.
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