RTF is a global modification that replaces all towns in the game.

Interesting idea! There's a guitar model from S.T.A.L.K.E.R. available online; we could create a bard unit for April Fool's Day.

We could extract a lute from Mount & Blade.
If we put in some effort, we could also find instruments in Skyrim, but it's difficult for someone who isn't familiar with modding. Most likely, you can find the item ID in the game, use special programs to locate the item and the model associated with it, but I don't know how to do that. I search manually by browsing through files.

There's also a flute made from a femur bone, but I'm afraid it has too many polygons – the game is new, and it's about undead creatures.