First, on polar bears, you will never see a gain in the mid 70's skill except for maybe a guaranteed gain (aka GGS), but I doubt you'll see even that. You can test it though by going to test center, duplicating only your music and discord skill and discording exactly one polar bear. If you gain, then gain is possible and you should still move on to something more difficult to discord after you're done checking to see if you have skills marked "down" on your skill list.
If you don't gain, then skill gain is impossible and you should move down the list of things to discord. I'd try gaman myself.