SA3_VOL_R
ym_mute(sc, SA3_VOL_R, sc->master_mute);
ym_mute(sc, SA3_VOL_R, 1);
ym_mute(sc, SA3_VOL_R, sc->master_mute);
ym_write(sc, SA3_VOL_R, (ym_read(sc, SA3_VOL_R) & ~SA3_VOL_MV) | atten);
val = SA3_VOL_MV & ~ym_read(sc, SA3_VOL_R);
ym_mute(sc, SA3_VOL_R, sc->master_mute);