It does not seem possible to change the name for music disk tracks through the language file, or any other way.
The music disc item itself can be renamed, but not the various tracks on them.
Since it is possible to change the songs on the discs, but the song titles still appear as the titles to the original songs by c418, i believe this to be a bug.
Linked issues
Comments 2
Duplicate of MC-19021
Can confirm.
You can't change the lore of the Music Discs.