I have a few other mods installed and custom NPCs will use the sounds from them and the original sounds from Minecraft, but not it's own sounds or sounds installed from resource packs. Selecting them and clicking play does nothing but stop any music already playing.
When trying to fix this I did find that swapping my sound file in for one of the sound files in the other mods it would then play. This makes me think it's an initialization problem.
Is anyone else getting this issue in 1.9?