I would love if it was an option for bards to play custom files for music around. Being able to have your own custom tunes around would be really cool and immersive while around adventuring. Also ya, I know this is a feature that should be really low priority and added way later, but It would be so cool. Plus you could change it with the different instruments you choose as a bard in the beginning.
Some other stuff could also be for multiple bards to make a whole thing together with multiple instruments, but idk how that would work, but could be pretty cool.
Pretty cool example:
https://www.youtube.com/watch?v=y8WCY_5ggS0