I love the concept, and I'm excited that someone's willing to make something like this. However, I've played games like these (minus the horror part) for years now, and I have some comments to make on that aspect of the game.
The slow speed at which the notes go down the screen is a good base setting, but it can be hard to tell (especially when playing on both fields of play at once) when each note will be hit at a more precise measure. I feel that these things can be fixed with one of two options (although I personally would suggest both);
You can 1) Allow people to change the rate at which the notes go down (as I've found that as I played this game more, I've slowly began to find how slow it is difficult to play- very notably so with the more complex rhythms- and giving the ability to make the speed faster (and maybe even a little slower, I don't know) might make it more natural to play so people can focus on the aesthetics rather than trying to figure out which note goes where in real time. Although, to be fair, this is more of a general suggestion than anything else.
And 2) make the ticks on the sides of each of the rows of columns A) maybe a little more visible but mostly B) coordinate each side of them. At the moment they're off sync with each other, making one or both out of sync with the song itself. Although I can see why A might not be something you would want to add, I feel fixing B) could be a big help in letting players more smoothly play the game... so that they can get more scared. It's a win-win!
Another thing I've noticed is the alignment of each of the columns. Namely, that they're angled differently from each other. I don't think this would be much of a problem if they weren't angled away from each other - which also seems to be (in a way that hurts in terms of consistency) different in other stages/circumstances. Giving it a dynamic angle makes it look nicer, but maybe angle it differently...
Similarly, one of the frustrations I've had with this game is how far apart each row of columns is. But that's fine, it does well with fitting to how you can't see both of your hands so well when they're on different areas of the piano anyways. That was just something I'm mentioning on the side....... although maybe they could be a little closer together... or have the notes not come on the screen from horizontally opposite ends of the screen.
I really like this concept and I hope it does well, so keep up the good work(and sorry for the long comment)!