This is a bad escape game
The solution makes no sense. First of all, the clickable area on top of the piano is so small and precise that it's hard to find in the first place. Once you find it, there's nothing at all to indicate it's where the key is, and there's no logical reason to suspect you're supposed to put EVERYTHING together and then stick it back in the piano. Good escape games are made by having logical escapes that make sense. The escape in this game seems to rely on already knowing what to do. This is a bad escape game.