mute the master volume of your soundcard?

uses

 MMSystem;

function GetMasterMute(

 Mixer: hMixerObj;

 var Control: TMixerControl): MMResult;

 // Returns True on success

var

 Line: TMixerLine;

 Controls: TMixerLineControls;

begin

 ZeroMemory(@Line, SizeOf(Line));

 Line.cbStruct := SizeOf(Line);

 Line.dwComponentType := MIXERLINE_COMPONENTTYPE_DST_SPEAKERS;

 Result := mixerGetLineInfo(Mixer, @Line,

   MIXER_GETLINEINFOF_COMPONENTTYPE);

 if Result = MMSYSERR_NOERROR then

 begin

   ZeroMemory(@Controls, SizeOf(Controls));

   Controls.cbStruct := SizeOf(Controls);

   Controls.dwLineID := Line.dwLineID;

   Controls.cControls := 1;

   Controls.dwControlType := MIXERCONTROL_CONTROLTYPE_MUTE;

   Controls.cbmxctrl := SizeOf(Control);

   Controls.pamxctrl := @Control;

   Result := mixerGetLineControls(Mixer, @Controls,

     MIXER_GETLINECONTROLSF_ONEBYTYPE);

 end;

end;

procedure SetMasterMuteValue(

 Mixer: hMixerObj;

 Value: Boolean);

var

 MasterMute: TMixerControl;

 Details: TMixerControlDetails;

 BoolDetails: TMixerControlDetailsBoolean;

 Code: MMResult;

begin

 Code := GetMasterMute(0, MasterMute);

 if Code = MMSYSERR_NOERROR then

 begin

   with Details do

   begin

     cbStruct := SizeOf(Details);

     dwControlID := MasterMute.dwControlID;

     cChannels := 1;

     cMultipleItems := 0;

     cbDetails := SizeOf(BoolDetails);

     paDetails := @BoolDetails;

   end;

   LongBool(BoolDetails.fValue) := Value;

   Code := mixerSetControlDetails(0, @Details,

MIXER_SETCONTROLDETAILSF_VALUE);

 end;

 if Code <> MMSYSERR_NOERROR then

   raise Exception.CreateFmt('SetMasterMuteValue failure, '+

     'multimedia system error #%d', [Code]);

end;

// Example:

procedure TForm1.Button1Click(Sender: TObject);

begin

 SetMasterMuteValue(0, CheckBox1.Checked); // Mixer device #0 mute on/off

end;

---------------------------------------

mixerSetControlDetails

auxoutsetvolume 是控制CD音量的  

waveOutSetVolume 是控制波形的  

midiOutSetVolume 是控制FM或者是synthesizer

unit Volume;

interface

uses windows,mmsystem;

type  

   Tvolume=record

      left,right:word; // 取值范围 0--65535

   end;

procedure fillstruct(control:PMixerControl;var Cdetails:tMIXERCONTROLDETAILS);

function getpeak(control:PMixerControl;var peak:integer):boolean;

function setvolume(control:Pmixercontrol; volume:Tvolume):boolean;

function getvolume(control:Pmixercontrol; volume:Tvolume):boolean;

var

   mcontrols:array of array of array of PMixerControl; //mixer的数组,单声卡可以不用

   fmixerhandle:HMIXER;   //mixer的句柄

implementation

procedure fillstruct(control:PMixerControl;var Cdetails:tMIXERCONTROLDETAILS);

begin

   Cdetails.cbStruct:=sizeof(cdetails);

   cdetails.dwControlID:=Control.dwControlID;

   cdetails.cbDetails:=sizeof(integer);

   cdetails.hwndOwner:=0;

end;

function getpeak(control:PMixerControl;var peak:integer):boolean;

var

  details:TMixerControlDetailsSigned;

  cdetails:tMIXERCONTROLDETAILS;

begin

   Result:=false;

   if control.dwControlType<> mixercontrol_controltype_peakmeter then exit;

   cdetails.cChannels:=1;

   cdetails.paDetails:=@details;

   fillstruct(control,cdetails);

   result:=mixerGetControlDetails(fmixerhandle,@cdetails,MIXER_GETCONTROLDETAILSF_VALUE)=0;

end;

function setvolume(control:Pmixercontrol; volume:Tvolume):boolean;

var

   details:array[0..30] of integer;

   cdetails:tMIXERCONTROLDETAILS;

begin

   fillstruct(control,cdetails);

   cdetails.cChannels:=2;

   cdetails.paDetails:=@details;

   details[0]:=volume.left;

   details[1]:=volume.right;

   result:=mixerSetControlDetails(fmixerhandle,@cdetails,MIXER_GETCONTROLDETAILSF_VALUE)=0;

   volume.left:=details[0];

   volume.right:=details[1];

end;

function getvolume(control:Pmixercontrol; volume:Tvolume):boolean;

var

   details:array[0..30] of integer;

   cdetails:tMIXERCONTROLDETAILS;

begin

   fillstruct(control,cdetails);

   cdetails.cChannels:=2;

   cdetails.paDetails:=@details;

   result:=mixerGetControlDetails(fmixerhandle,@cdetails,MIXER_GETCONTROLDETAILSF_VALUE)=0;

   volume.left:=details[0];

   volume.right:=details[1];

end;

end.

// 调用方法:

procedure TForm1.Button1Click(Sender: TObject);

var  s : Tvolume;

    kz : Pmixercontrol;

begin

   new(kz); //<------------ 此处一定要分配内存

kz.dwControlID := 0;

s.left := 0;

s.right := 0;

try

setvolume(kz,s);

except

end;

freemem(kz);

end;