SRC: https://www.speedrun.com/hsp

You interact with a piano to haunt it and once the human character approaches it, it will start to play a creepy melody on its own. There are two pianos like this in the game in levels 3 and 4. The effect looks/sounds the same for either of them.

Evidence:

Without the players interaction, the piano would not play. Therefore the player themselves causes the piano to be played, if only indirectly. Therefore approved