As founder of the newly created "Ukulele Players of Ur" group, I was thinking that it would be fun to have a music-maker skill.
Using ukuleles as an example: They come in all shapes and colors, so it would be fun to collect/earn/buy different ones. There are also many types (soprano, tenor, baritone, banjo uke, etc.); different tunings; low G string, etc. - so lots of variety is possible.
I was also thinking that you could learn/earn chords, strum patterns and rhythms (similar to collecting cooking ingredients) - and maybe put those elements together to create tunes in a similar manner to how recipes work now. Then, once you have a tune in your inventory, you could play it for another player. Maybe there would even be a way to have a group play together (an in-world uke jam!). You could also sell ukulele cases where a ukulele, chords, tunes, etc. could be stored (like the spice rack).
And of course, the idea could be expanded to other instruments, as well. (Percussion instruments would be fun.)