uses ...., MMSystem;
procedure SendMCICommand(Cmd: string);
var
RetVal: Integer;
ErrMsg: array[0..254] of char;
begin
RetVal := mciSendString(PChar(Cmd), nil, 0, 0);
if RetVal <> 0 then
begin
{get message for returned value}
mciGetErrorString(RetVal, ErrMsg, 255);
MessageDlg(StrPas(ErrMsg), mtError, [mbOK], 0);
end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
SendMCICommand('open waveaudio shareable');
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
SendMCICommand('close waveaudio');
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
SendMCICommand('play "c:\a.wav"');
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
SendMCICommand('play "c:\b.wav"');
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
SendMCICommand('play "c:\c.mp3"');
end;