Default songs on car stereo

hi, I have a car that only accepts usb flash drives to play songs, when I connect my s4, it won't recognize any folders.

so I installed drivedroid, created a blank image and copied some songs into it, so my car will recognize this folder as a mass storage device, and now it's working.

problem is that I have some songs on my music folder, and had to copy the same songs into drivedroid's image.

is there a way to access the folder that drivedroid creates from the phone itself, so I can use the music player with it?
where's that folder located?

thanks