I'm sure that I am in the minority, but I am excited for Harmonism to come out. I know it will be awhile since there are other magic schools more people would like to see. I have a suggestion for it when it eventually does. A musical instrument I would like to see is the Guzheng. (aka "Chinese Zither"). It could be the Khurite themed instrument. Picture inserted for reference.
I personally do really love Guzhengs.
However, I think for
Harmonism we may have to consider what instruments will be easy to carry and play while standing. They'll have to be portable and not look goofy for players to be taking them off of their backs and playing them, and a guzheng suddenly being set up would kind-of be like someone lugging around a xylophone or an electric keyboard in terms of weight/size. If you look at the list of scrolls they had in mind for harmonism, they're definitely meant to be used around enemies.
I think that a furniture class of playable items could be interesting, though. And in that case a guzheng (or something similar to one, I could see Khurites of Morin Khur maybe making a
yatga, which is a very similar concept) could work really well for that. (I also would love to see some ambient NPCs who play Morin Khuurs,
this particular combination of Morin Khuur and Ikh Huur is actually really great. Very haunting and melancholy melody.)