MMRESULT   rc;                             //   Return   code.
              HMIXER   hMixer;                         //   Mixer   handle   used   in   mixer   API   calls.
              MIXERCONTROL   mxc;                   //   Holds   the   mixer   control   data.
              MIXERLINE   mxl;                         //   Holds   the   mixer   line   data.
              MIXERLINECONTROLS   mxlc;       //   Obtains   the   mixer   control.

              //   打开mixer.   单声卡的deviceID为0.
              rc   =   mixerOpen(&hMixer,   0,0,0,0);
              if   (MMSYSERR_NOERROR   !=   rc)   {
                      //   Couldn't   open   the   mixer.
              }

              //   初始化MIXERLINE结构体.
              ZeroMemory(&mxl,sizeof(mxl));
              mxl.cbStruct   =   sizeof(mxl);

              //   指出需要获取的通道，扬声器用MIXERLINE_COMPONENTTYPE_DST_SPEAKERS
              mxl.dwComponentType   =   MIXERLINE_COMPONENTTYPE_DST_SPEAKERS;

              rc   =   mixerGetLineInfo((HMIXEROBJ)hMixer,   &mxl,
                                                            MIXER_GETLINEINFOF_COMPONENTTYPE);
              if   (MMSYSERR_NOERROR   ==   rc)   {
                      //   Couldn't   get   the   mixer   line.
              }

              //   取得控制器.
              ZeroMemory(&mxlc,   sizeof(mxlc));
              mxlc.cbStruct   =   sizeof(mxlc);
              mxlc.dwLineID   =   mxl.dwLineID;
              mxlc.dwControlType   =   MIXERCONTROL_CONTROLTYPE_VOLUME;
              mxlc.cControls   =   1;
              mxlc.cbmxctrl   =   sizeof(mxc);
              mxlc.pamxctrl   =   &mxc;
              ZeroMemory(&mxc,   sizeof(mxc));
              mxc.cbStruct   =   sizeof(mxc);
              rc   =   mixerGetLineControls((HMIXEROBJ)hMixer,&mxlc,
                                                                    MIXER_GETLINECONTROLSF_ONEBYTYPE);
              if   (MMSYSERR_NOERROR   !=   rc)   {
                      //   Couldn't   get   the   control.
              }

              //   获取控制器中的值的音量范围：mxc.Bounds.lMinimum到mxc.Bounds.lMaximum.

              MIXERCONTROLDETAILS   mxcd;                           //   Gets   the   control   values.
              MIXERCONTROLDETAILS_SIGNED   volStruct;   //   Gets   the   control   values.
              long   volume;                                                     //   Holds   the   final   volume   value.

              //   初始化MIXERCONTROLDETAILS结构体
              ZeroMemory(&mxcd,   sizeof(mxcd));
              mxcd.cbStruct   =   sizeof(mxcd);
              mxcd.cbDetails   =   sizeof(volStruct);
              mxcd.dwControlID   =   mxc.dwControlID;
              mxcd.paDetails   =   &volStruct;
              mxcd.cChannels   =   1;

              //   获得音量值
              rc   =   mixerGetControlDetails((HMIXEROBJ)hMixer,   &mxcd,
                                                                        MIXER_GETCONTROLDETAILSF_VALUE);
              if   (MMSYSERR_NOERROR   ==   rc)   {
                      //   Couldn't   get   the   current   volume.
              }
              volume   =   volStruct.lValue;

      volStruct.lValue   =   25000; //想要设置的值
      rc   =   mixerSetControlDetails((HMIXEROBJ)hMixer,   &mxcd,
      MIXER_SETCONTROLDETAILSF_VALUE);