If I may, does your CD player support the mp3 format, or is the CD player looking for.....well....music?
MP3 is data, and your CD player, is a cd player. MP3 is not music.
Just poking at it...too many variables. Does the CD player receive AM and FM signals as well? if so, it cannot "read" an MP3 Data disk.
Now, let us say that the cd does support the MP3 format, then the disk isn't closed.