Play a music disc, then either change the resource packs you have loaded or press F3+T to reload the resource packs. The music disc will stop playing and you have to eject and place it again in order to hear it.
Linked issues
is duplicated by 9
MC-192344
Jukebox stopped playing
Resolved
MC-200121
Minecraft music stops for a period of time after reloading
Resolved
MC-254548
Music stops upon performing an intensive task
Resolved
MC-264407
Jukebox Stops Playing when Reloading Resource Packs
Resolved
MC-264523
Summoning a warden and then loading a resource pack cancels out the digging sound
Resolved
4 more links
This is intentional, the whole sound engine gets restarted when you load a resource pack, or do F3+T, furthermore, the resource pack may change the music.