Alright, I've restarted this 3 times but never managed to progress much.
First time, I went left first after finding the flashlight and immediately found the room where you get locked inside. The one with the writing on the wall that says "The Tune Calms Me". I found that I couldn't interact with anything inside the room until I checked the door again, discovered they are locked and got the "Find The Way Out" objective.
There's nothing in the lockers and nothing in the desk drawer either. There's a guitar next to the piano that I can pick up, but I don't seem to be able to do anything with it. I can interact with the piano and play music on it, but there's nothing that says what I should be playing. There's writing on the wall saying "The Tune Calms Me" but nothing about what tune it is and how to play it.
There's some torn paper on the desk, but all it says is how to get a key to some room on the second floor, it's incomplete, one part is missing. And you can't even go to the second floor yet, so it's useless. After trying everything, including pressing random keys on the piano, I restart since I can't leave the room.
Alright, this time I go right, thinking that I was supposed to go there first. In one room on the right, there's a piano that plays some song on its own. There's also a room with a paper that tells you the second part of the way to get the key to the second floor room. You still can't go to the second floor, so useless. I get locked inside the "The Tune Calms Me" room again and can't figure out what to do either. So, another restart.
Third time, I go to the third room on the left that I missed the first time. Maybe there's something there? Nope, empty. I already checked everywhere else, so dunno what to do next.
I think that the song that the piano is playing in the room on the right is what you are supposed to play in the "The Tune Calms Me" room. If that's the case, the puzzle is WAY too hard. First off, if you aren't knowledgeable in music, you won't know which keys you need to hit on the piano to reproduce it.
Second, the tune is really long, so it's not really something you can memorize easily. Third, since you get locked inside the room, you can't even backtrack to the piano that plays the tune on its own to refresh your memory. Fourth, there are no hints as to what tune you should be playing at all or even some hint that makes it easier for the players that are not familiar with playing the piano.
If you go left before going right and enter that "The Tune Calms Me" room, you get locked inside before you even had a chance to hear that piano playing. IF I'm right and this is what the puzzle is, then it needs to be revamped.
Also, the key in the drawer inside the starting room blends too much with the texture of the drawer, so at first I didn't notice that there's anthing inside. I suggest you give it a slightly brighter color so that it stands out more. The guitar in the "The Tune Calms Me" room also seems to have the same texture as the walls and it doesn't look good.
Anyway, I enjoyed what I played and I'd certainly play more if I knew how to progress. This game seems like it has potential to be very good!