Basically wanted to suggest something that may or may not already be on the list. Basically posting this in the context & example of Star Wars Galaxies use of entertainer & Cantina; Phantasy Star Online 2 use of instruments; Animal Crossing: New Leaf's DJ area at night.
Basically wanting to suggest NPCs being able to learn music while also being able to perform for you when reading from sheet music. You'd be surprised how popular or fun composing music is in these sorts of games. Any game really. I'm recommending the following to also compress the space that Minecraft wasted with the music blocks into something that's more into paper, menus, and NPCs.
1) NPC Musicians: It be sweet if we could teach musicans to play for us at a cantina when the players won't be able to. Just hand the NPC a sheet music they'll use as a request to then make them play for you. Would be overly handy to do this from a conductor NPC who controls the other NPC holding instruments to play a mini-concert to an orchestra. They would put on performances for us players. Compared to Minecraft, they would be a condensed form of music blocks.
2) Sheet music: Basically using the book feature in this game by also allowing us to write down the instrument's key presses when timed for the NPCs to play it out themselves for us. This would spawn live concerts, cantina builds, and etc by also having those on servers hear other people's taste in music.
Seeing the piano has me assuming that Red51 shall eventually expand on the instrument choices to add trumpets, violins, trumbones, drums & etc. I'm also wanting to eventually find myself building a "Sharatang Concert Hall" that I failed to do in Minecraft thanks to how blocky the music blocks would be. WIth how powerful Rising World is this would be a proper place to take advantage of in a vanilla manner. More so in a modded manner.
Now suggesting this lightly with the main mood now gone. Still posting it for future inspiration.