Noted today that while grip could access the CD drive on my machine, clemetine-player and xfburn could not.

Figure out which device node your CD drive is with camcontrol:

camcontrol devlist | grep cd
at scbus4 target 0 lun 0 (cd0,pass2)

Simply add the following to /etc/devfs.conf and restart devfs to get access to the CD device:

perm /dev/cd0 0666
perm /dev/xpt0 0666
perm /dev/pass2 0666

Now bear in mind, that this means any user of your machine has access to the device now. Hopefully, on a desktop computer, you know all the users of your machine.