Workaround:

1. Load the DeSmuME_2010 File on VC++ 2010 Express.

2. On the left pane, right click where it says DeSmuME_VS2010.

3. On the menu that will pop up, go to Add > Existing Item...

4. Browse to the following folder: "path to desmume svn/src/addons/" and find there the piano.cpp file and double click it.

5. On the top menu bar, click on "Debug" and click on "Build".

DONE

(Sorry if my instructions weren't clear, I'm mexican)