hkey_sound_mute
static hkey_fn_t hkey_sound_mute;
{"sound_mute", hkey_sound_mute},
hkey_sound_mute(sc->handle, HKEY_SET, &mute);
hkey_sound_mute(h, HKEY_GET, &arg);
hkey_sound_mute(h, HKEY_SET, &arg);