After some reflection, I have decided to rewrite this post. The original provided little feedback and was more of a creative expression.
Note for the Lightless is a powerful game concept. It presents a world that requires a calm, gentle but strong demeanor to navigate. It teaches you how to be comfortable with your own voice. It shows what giving gives depending on who you give to. It encourages you to listen.
If this game were to be expanded upon, my suggestion (which my original post was inspired from) would be to have an antagonist (deep, male voice) that warns the player of the dangers of the lightless ones. I feel this would add to the worldbuilding in that the narrative follows the scene instead of being derived from an outer perspective about human greed. It would make the darkness unsettling as your perception of these creatures starts with fear. It would add a lot to the experience having two higher voices (one encouraging, and one discouraging) speak to you through verse as you sing to the creatures.
I also support the idea of everything being extremely dark. You could use bioluminescence to light the path you walk and create a radial wave when you sing. Maybe this wave brings the creatures to you instead of them being stationary. Maybe the volume of your voice allows it to spread farther. This as a game mechanic would create a layer of difficulty and uncertainty about what will show up. Perhaps there are bioluminescent marks on the creatures that make them look terrifying until you sing their note, revealing the cute, glowing forms that we see in the jam version.
I was inspired to sing and write poetry because of this game and its star developer. I need games like this. Thank you for making it. Let's make more of them!