Play an mp3 file in a subfolder via mcisendstring

Question

make mcisendstring to play a file in subdirectory

I have a little problem with mcisendstring. I know you can open a text file in a subdirectory like this:

ofstream file(".\\subfolder\\file.txt");

but in mcisendstring that doesn't work I have the exe file in a folder called main and the music in a subfolder called music. It would be .\\music\\song.mp3 but that doesn't work visual studio won't let me create a subfolder for resources. What do I do?