Harmony is a library that is used by other mods, just like Hugslib but different. Before version 1.1 this library was included in those mods and there was no need to load it as a separate mod. However, version 1.1 changed this and including it in every mod is no longer possible and it needs to load separately before anything else. Including before the Core game itself. So place this mod all the way on top of the load list *BEFORE* core.
Harmony Library Review
Once included on a per mod basis, the Harmony Library must now be added to the game manually. So many mods ended up using this library, that it is a must-have for all players. If you’re a casual player, you need not worry about what it does… it simply offers solutions for modders.