OPL3_REG_FNUM_LOW
opl3_reg = OPL3_LEFT | (OPL3_REG_FNUM_LOW + voice_offset);
opl3_reg = reg_side | (OPL3_REG_FNUM_LOW + voice_offset);
opl3_reg = reg_side | (OPL3_REG_FNUM_LOW + voice_offset);
opl3_reg = reg_side | (OPL3_REG_FNUM_LOW + voice_offset);