I just figured out something about audio priority on these Nokia devices.
If you playback audio with EMdaPriorityMax, your audio will prevent ringtones coming through on the Nokia 6630.
But if you set it to EMdaPriorityNormal, your sound will be interupted by the keytones on the 6680 and 6681.
It took me a while to figure out why my sound kept being interrupted. But this was it.
Now, with priority 70 it works as expected. like on earlier Nokia phones like the 6600 and 6670.