You can´t change the ingame music with recource packs
What I expected to happen was that you hear your music of the recource pack
What actually happened was that the normal Minecraft music was played e.g. with Disks... By Disks is the text e.g. "records.13"
Duplicate of MC-36791 - If you have not, please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.