I'm envisioning a sort of thing where you have to go to a specific spot on an island and start playing your instrument. Ghostly music notes appear and form a path and only stay out as long as you're playing. You'll want to follow the path and grab all the notes, but you've only got until the end of the song to gather them all up, so you're speed limited and can't use any other movement tools... but having multiple people would help, since you could have some people playing and some people collecting notes and such.
And at the end of the trail is a treasure chest or some other type of reward or some such.
It's sort of an extension of that first bilge rat adventure with the Meg, where you had to carry the tune... but on a much smaller scale.
Though I could see it being expanded to cross to other islands at higher ranks. Which would almost certainly require a crew of some size, just for keeping the song going while also boarding the ship logistics.
Just the basic outline of an idea, but I thought it good enough to share with you fine folks.
