Read access for mopidy user on /media

Hallo Community,

I’am running Mopid on a Rasberry Pi (Rasperian) as system service. My Musik is saved on an USB device which is pluged in (FAT32).
The documentation says that I have to give the mopidy user read access to my local musik which is my USB device.

My Problem is that I can’t find out how I give this read access.
I have tried chmod 777 and added mopidy to the plugdev group with no results.

So can you give me an advice how do i do this?

I am glad about any kind of help!

I avoid this problem now my running mopidy as user program and autostart mopidy with an entry in crontab -e.