As 1.1 has arrived to shadecrest so do new music disks. However, we can't legitimately acquire music disk 11 as we do not have any 1.1 dungeon/stronghold chests in the world. And I would love to have it just for the heck of it to feed the collector in me. This could be done by something such as trading in some music disks or simply buying it in the admin shop when it returns.
Since the mining world isn't going to be reset soon (i personally operate under the view that it will never be reset since that's the safest and most likely option) and that would be the only way to get disc 11, that would make it an item that can only be acquired by spawning it in and well within the realm of what the admin shop supplies. When/if the mining world is reset then the chest that sells the disc could be changed to something else or removed altogether. comment about near-future mining world reset chances being non-existent are not intended to be shots at people but my honest opinion based on what i have heard/read on the subject.
I feel that it would be a better idea to maybe have a special way like a requirement to get one or something, like my earlier suggestion to trade a certain amount of the other disks to get disk 11. I feel this would be a cool way of getting it.