I like the idea of this game, and rhythm games are notoriously difficult to make, so cheers for the attempt!
There doesn't seem to be any consequence for missing beats... I ended up just letting off the keyboard completely to see "what would happen" and, well, nothing happens. The game lacks a losing condition.
Good notion to sneak your tutorial in the "pull the book out of the shelf" moment, but it lasted just a little too long to not get tedious after the first couple of book pulls.
The music choice was good and fit the art theme of the lone musician among bookshelves.
The music scores could benefit from a "scores remaining" counter of some sort. The "next score"/"score replacement" animation had a bad habit of disappearing with notes still in between them, making it hard to follow the start and end of each score. There was one song that started with notes too close to the "push arrow to begin" phase, making them impossible to actually hit.