I (unfortunately) recently installed the Belle OS on my C7-00. I have all of my music on a 16 GB Micro SD card, and have had no problems in playing the music on the handset.
There are 126 albums currently on the Micro SD, however when I connect the phone to the laptop and try to play the music through Windows Media Player, it only shows 7 albums in total.
They are the same 7 albums every time, and the same result is shown whether I choose the 'file transfer' or 'Nokia Suite' options.
I ripped the music (from CD's) using Windows Media Player, then basically copy and pasted the files onto the Micro SD. I didn't use WMP's sync feature because I have found it to be unreliable most of the time.