Hello!
I'm a Java developer and I just created a plugin for my own server I play with some friends.
You can find my plugin in https://www.spigotmc.org/resources/custom-songs.81865/
Description: It allows you to add custom songs (as music discs) to Minecraft using your own texturepack without replacing default Minecraft sounds.
The plugin is currently in development and the ability to add custom songs is currently disabled to the public. Once I fix all the bugs I'll enable this again but for now I'd love to test it with my friends.
Thanks a lot.