I won’t finish this game, but as it still raises some interest I will publish a walkthrough, as there are some things you can do in Nault Nipp, other than the glitchy events.

Spoilers ahead.
The piano is missing music, the Note Books scattered around the village.

1) The Piano is floating in the future, bring it back to the present by using the clock in the Clockhouse.
2) Now you can access it and try to play it. You need to push the Note Books close to the Piano just by walking with them ahead of you.
3) First book is in the Clockhouse, kick it through the door and push it close then listen to the altered tune of the Piano.
4) Second book is just next to the Piano.
5) Third book is next to the houses where you start.
6) Fourth book is on a house, you need to jump really high in order to get it.
7) Solution is visiting the Gravity’s Eye close to the mountains on the east.
8) Block it’s visible path with the house that moves and very thin.
9) Now you can jump high enough to get the last book.
10) Enjoy the tune.

There are several in-game hints about these things, especially in the Hint Room, the door standing alone leads to it and you can access pictures on the wall by moving the door and visiting the Hint Room.