The IDirectMusicBuffer::TotalTime method returns the total time spanned by the data in the buffer.
HRESULT TotalTime(
  LPREFERENCE_TIME prtTime
);
 If the method succeeds, the return value is S_OK.
If it fails, the method may return E_POINTER.
  Windows NT/2000: Requires Windows 2000.
  Windows 95/98: Requires Windows 95 or later. Available as a redistributable for Windows 95.
  Header: Declared in dmusicc.h.