The IDirectMusicPort::UnloadInstrument method is used to unload a previously downloaded DLS instrument.
HRESULT UnloadInstrument(
  IDirectMusicDownloadedInstrument *pDownloadedInstrument
);
 If the method succeeds, the return value is S_OK.
If it fails, the method may return one of the following error values:
| DMUS_E_NOT_DOWNLOADED_TO_PORT | 
| E_POINTER | 
| E_NOTIMPL | 
This method must be called in order to free memory allocated by IDirectMusicPort::DownloadInstrument.
  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.