PURPOSE: To vary the varying speed of sound image localization according to the pitch of a musical performance.

CONSTITUTION: The read period of a ROM 207 which is transferred from a CPU according to the pitch of the musical performance is converted by a converting circuit 205 into a specific value, which is compared by a comparing circuit 203 with the value of a counter 202 which counts the clock generated by a basic clock circuit 201. Each time the both match each other, the comparing circuit 203 outputs '1', an address counter 204 is made to count up, and the counter 202 is reset. Each time the address counter 204 generates its output, a sound volume coefficient which continuously varies is read out of the ROM 207 and a sound volume coefficient which varies reversely to the variation is generated by a coefficient converting circuit 209, so that a sound source signal is multiplied by them. The multiplication results are sent to an L-channel amplifier and an R-channel amplifier.