PURPOSE: To perform frequency setting in delicate fashion and to recognize frequency characteristic at a glance.

CONSTITUTION: A CPU 32 displays a display indicator 44 of slide volume shape on a display part 38. The display indicator 44 can be moved in the horizontal direction by the operation of an operating part 39, and a knob part 48 in the display indicator 44 can be moved in the vertical direction by the operation of the operating part 39. The CPU 32 decides the gain of frequency in the characteristic of a parametric equalizer consisting of a DSP 30 corresponding to the position in the vertical direction of the knob part 48 based on the position in the horizontal direction of the display indicator 44, and decides a parameter in accordance with decided frequency characteristic, and supplies it to the DSP 30.