Would be awesome to have a little drone then follow you or you can put somewhere and which can play the song you want with the instrument you want... even be able to do a band with him so... even in single player you would be able to do song with multiple instrument. That would be a great way to put atmosphere in a specific place, during an even (like a dual with an other player) or if you want to travel on a planet with a choose music without have to worry to be interrupt by those damn monsters.
But that would defeat the purpose of finding more instruments. I actually enjoy that aspect. Though with that in mind, I do have a suggestion to make on top of yours, since I like the idea of being able to play music without having to actively use your instrument. You could make it work similar to the 3d printer: you can have the droid 'scan' instruments you've already found, and it will be able to replicate its sounds anytime. It could even build any instruments you had it scan. That way, you and your friends could collect and trade instruments!
I am not a graphic guy, sorry. Well, maybe make the drone being able to equip the instrument so only the already find instrument could be play.
How about something close to a floating jukebox? I think that would look really cool, and could actually act like a pet. Possibly a dungeon item that you can also craft (expensivley) in the 4th tier (?). It would be quite interesting.
Sort of, the core cows is more than likely a bit more of a challenge to figure out, but it'll be an easy translation. Thanks for the idea