Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

{ 
  The following example demonstrates getting and setting the volume 
  for the first CDAudio and LineIn device found. Note that both left and 
  right 
  channels are supported. The volume range is from 0 to 65535. 

  Example: 
}

 uses
   MMSystem;

 function GetLineInHandle(AudioType: Integer): Integer;
 var
   i: Integer;
   AudioCaps: TAuxCaps;
 begin
   Result := 0;
   for i := 0 to auxGetNumDevs - 1 do
    begin
     auxGetDevCaps(i, @AudioCaps, SizeOf(AudioCaps));
     if AudioCaps.wTechnology = AudioType then
      begin
       Result := i;
       Break;
     end;
   end;
 end;

 procedure TForm1.Button1Click(Sender: TObject);
 var
   v: DWORD;
 begin
   AuxGetVolume(GetLineInHandle(AUXCAPS_CDAUDIO), @v);
   Edit1.Text := IntToStr(LoWord(v));
   Edit2.Text := IntToStr(HiWord(v));
 end;

 procedure TForm1.Button2Click(Sender: TObject);
 var
   v: DWORD;
 begin
   v := MakeLong(Word(StrToInt(Edit1.Text)),
     Word(StrToInt(Edit2.Text)));
   AuxSetVolume(GetLineInHandle(AUXCAPS_CDAUDIO), v);
 end;

 procedure TForm1.Button3Click(Sender: TObject);
 var
   v: DWORD;
 begin
   AuxGetVolume(GetLineInHandle(AUXCAPS_AUXIN), @v);
   Edit3.Text := IntToStr(LoWord(v));
   Edit4.Text := IntToStr(HiWord(v));
 end;

 procedure TForm1.Button4Click(Sender: TObject);
 var
   v: DWORD;
 begin
   v := MakeLong(Word(StrToInt(Edit3.Text)),
     Word(StrToInt(Edit4.Text)));
   AuxSetVolume(GetLineInHandle(AUXCAPS_AUXIN), v);
 end;