I'm experiencing similar confusion. I've collected about 10 music discs from creepers, and all are either cat or 13. This is in an SMP server that started in 1.8. Can anyone report seeing new music discs drop in 1.0? Or are the new discs only in chests? Or am I just absurdly unlucky?
Yeah I got about 40 discs during 1.9 from my exp grinder and they were all the 2 that have always been in the game. All the other discs are in creative only, and eventually mojang will implement them into survival