A sound source setting section and a listening setting section are each configured to have a parameter setting section, a display section, and an arrangement relocation section on a placing surface of a placing table in real space, the arrangement relocation section allowing the source setting and listening sections to relocate on the placing surface. A reflecting member to which a reflecting characteristic is assigned is configured to be placeable on the placing table. A mixing process section performs a mixing process and also generates an image at the position, in a virtual space, of the sound source setting section relative to the listening setting section, the image having a texture indicative of a sound source assigned to the sound source setting section. Sound mixing with respect to a free listening point is thus performed easily.