=== Microsoft Synthesizer ===

Is this helps u?

 from http://www.delphi-fundgrube.de/faq13.htm


uses
  MMSystem;

procedure MakeSound(Frequency, Duration : integer);
{writes tone to memory and plays it}
var
  WaveFormatEx : TWaveFormatEx;
  MS           : TMemoryStream;
  i, TempInt,
  DataCount,
  RiffCount    : integer;
  SoundValue   : byte;
  w            : double; // omega ( 2 * pi * frequency)
const
  Mono       : Word = $0001;
  SampleRate : integer = 11025; // 8000, 11025, 22050, or 44100
  RiffId     : string = 'RIFF';
  WaveId     : string = 'WAVE';
  FmtId      : string = 'fmt ';
  DataId     : string = 'data';
begin
  with WaveFormatEx do begin
    wFormatTag := WAVE_FORMAT_PCM;
    nChannels := Mono;
    nSamplesPerSec := SampleRate;
    wBitsPerSample := $0008;
    nAvgBytesPerSec := nSamplesPerSec * nBlockAlign;
    nBlockAlign := (nChannels * wBitsPerSample) div 8;
    cbSize := 0;
  end;
  MS := TMemoryStream.Create;
  with MS do begin
    {Calculate length of sound data and of file data}
    DataCount := (Duration *  SampleRate) div 1000;  // sound data
    RiffCount := Length(WaveId)
                 + Length(FmtId) + SizeOf(DWord)
                 + SizeOf(TWaveFormatEx)
                 + Length(DataId) + SizeOf(DWord)
                 + DataCount; // file data
    {write out the wave header}
    Write(RiffId[1], 4);                        // 'RIFF'
    Write(RiffCount, SizeOf(DWord));            // file data size
    Write(WaveId[1], Length(WaveId));           // 'WAVE'
    Write(FmtId[1], Length(FmtId));             // 'fmt '
    TempInt := SizeOf(TWaveFormatEx);
    Write(TempInt, SizeOf(DWord));              // TWaveFormat data size
    Write(WaveFormatEx, SizeOf(TWaveFormatEx)); // WaveFormatEx record
    Write(DataId[1], Length(DataId));           // 'data'
    Write(DataCount, SizeOf(DWord));            // sound data size
    {calculate and write out the tone signal}   // now the data values
    w := 2 * Pi * Frequency;  // omega
    for i := 0 to DataCount - 1 do begin
      // wt = w *i /SampleRate
      SoundValue := 127 + trunc(127 * sin(i * w / SampleRate));
      Write(SoundValue, SizeOf(Byte));
    end;
    // you could save the wave tone to file with :
    // MS.Seek(0, soFromBeginning);
    // MS.SaveToFile('C:\MyFile.wav');
    // then reload and play them without having to
    // construct them each time.
    {now play the sound}
    sndPlaySound(MS.Memory, SND_MEMORY or SND_SYNC);
    MS.Free;
  end;
end; {Alan Lloyd}

Sorry, I asked about MIDI, not WAVE audio. Anyway thanks... I got answer from www.programmersheaven.com. Seems I need DirectMusic to use MS Synthesizer, so need DirectX headers:

//plays normal midi or SGT/SGP(DirectMusic Producer) files
procedure PlayFile(FileName: string);
var
Name: string;
Path: string;
begin
Name := ExtractFileName(FileName);
Path := ExtractFilePath(FileName);
DMusicLoader.SetSearchDirectory(GUID_DirectMusicAllTypes,StringToOleStr(Path),True);
DMusicLoader.LoadObjectFromFile(CLSID_DirectMusicSegment,IID_IDirectMusicSegment8,StringToOleStr(Name),DMusicSegment);
if ExtractFileExt(Name) = '.mid' then
DMusicSegment.SetParam(GUID_StandardMIDIFile,$FFFFFFFF,DMUS_SEG_ALLTRACKS,0,nil);
DMusicSegment.Download(DMusicPerformance);
DMusicPerformance.PlaySegment(DMusicSegment,0,0,nil);
end;

OK no problem
:-)