I've noticed that a music pack I made is playing certain tracks in broad daylight on the surface, despite the category being set to 'cave' and only 'cave'. The complete file for the music is here, created using 'LOTR Music Pack Creator Beta 3.5':
{"tracks":[{"file":"cave ambience 1.ogg","title":"Cave Ambience","regions": [{"name":"all","categories":["cave"]}]}, {"file":"cave ambience 2connum_.ogg","title":"Cave Ambience 2","regions":[{"name":"all","categories":["cave"]}],"authors":["Connum"]}, {"file":"cave ambience 3 everythingsounds.ogg","title":"Cave Ambience 3","regions":[{"name":"all","categories": ["cave"]}],"authors":["EverythingSounds"]}, {"file":"cave ambience 4 by 150134.ogg","title":"Cave Ambience 4","regions":[{"name":"all","categories":["cave"],"weight":0.5}]}]}
As you can see, the regions for the tracks are set to 'all', and the categories set to 'cave'.
Note: this was used with one other music pack in the 'lotrmusic' folder.