Initially I wanted to have the typical ambient low rumbling noise soundtrack rather than actually having 'real' music. This is pretty easy and also cheap to do and it usually works very well for a horror game.
However, after a while I was getting really worried about the whole arc and the mood of the game. So here I have a very dark visual look, a mature and horrific story and I added a low and depressing scary soundtrack underneath. Playtesters felt exhausted and drained pretty fast.
I tried several things with timing, the visuals and eventually also decided that I should try different things with the music as well.
I'm not equipped with the proper equipment to whip up an orchestral soundtrack. What I had at hand was a inexpensive small handheld audio recorder (a Zoom H1 from Sony for about a 100 USD) and an old piano. So I sat down and started improvising, not only doing scary tracks but also uplifting ones. I added a bit of reverb and put one of them into the game, replacing the scary ambient one.
I was excited! This was an easy way to add (the much needed!) contrast to the game. In my opinion it gets old rather quickly if you, let's say, add sadness to sadness.
The other thing I did was to contact a friend who is a a great guitar player and composer. He said he'd love to do music for games for a change and contributed some awesome tracks.
Here's an old/new comparison. The first track is what I initially had:
Here's the second take which I ended up using:
Don't get me wrong - there's still plenty of noisy low rumbling. But there are airy, light tracks as well.