I think Wurm Online could benefit from the addition of a few instruments such as guitar variations such as the Oud or wind instruments like a simple Flute.
With musical instruments, I'd imagine there could be a new skill to play them as well as one for composition. Perhaps musical scripts could be written in some in-game interface that transfers notes, octaves, tempo, etc. to some sort of copy and shareable scroll to be attempted by someone else far away.
I know I would spend hours chipping away at songs, but it certainly wouldn't be for everyone.