uses
 MMSystem;

 function GetWaveVolume(var LVol: DWORD; var RVol: DWORD): Boolean;
 var
 WaveOutCaps: TWAVEOUTCAPS;
 Volume: DWORD;
 begin
 Result := False;
 if WaveOutGetDevCaps(WAVE_MAPPER, @WaveOutCaps, SizeOf(WaveOutCaps)) = MMSYSERR_NOERROR then
 if WaveOutCaps.dwSupport and WAVECAPS_VOLUME = WAVECAPS_VOLUME then
 begin
 Result := WaveOutGetVolume(WAVE_MAPPER, @Volume) = MMSYSERR_NOERROR;
 LVol := LoWord(Volume);
 RVol := HiWord(Volume);
 end;
 end;


 { 
 The waveOutGetDevCaps function retrieves the capabilities of 
 a given waveform-audio output device. 

 The waveOutGetVolume function retrieves the current volume level 
 of the specified waveform-audio output device. 
}


 function SetWaveVolume(const AVolume: DWORD): Boolean;
 var
 WaveOutCaps: TWAVEOUTCAPS;
 begin
 Result := False;
 if WaveOutGetDevCaps(WAVE_MAPPER, @WaveOutCaps, SizeOf(WaveOutCaps)) = MMSYSERR_NOERROR then
 if WaveOutCaps.dwSupport and WAVECAPS_VOLUME = WAVECAPS_VOLUME then
 Result := WaveOutSetVolume(WAVE_MAPPER, AVolume) = MMSYSERR_NOERROR;
 end;

 { 
 AVolume: 
 The low-order word contains the left-channel volume setting, 
 and the high-order word contains the right-channel setting. 
 A value of 65535 represents full volume, and a value of 0000 is silence. 
 If a device does not support both left and right volume control, 
 the low-order word of dwVolume specifies the volume level, 
 and the high-order word is ignored. 
}


 { *** How to Use: ***}

 // SetWaveVolume: 

procedure TForm1.Button1Click(Sender: TObject);
 var
 LVol: Word;
 RVol: Word;
 begin
 LVol := SpinEdit1.Value; // max. is 65535 
 RVol := SpinEdit2.Value; // max. is 65535 
 SetWaveVolume(MakeLong(LVol, RVol));
 end;


 // GetWaveVolume: 

procedure TForm1.Button2Click(Sender: TObject);
 var
 LVol: DWORD;
 RVol: DWORD;
 begin
 if GetWaveVolume(LVol, RVol) then
 begin
 SpinEdit1.Value := LVol;
 SpinEdit2.Value := RVol;
 end;
 end;