Georg,
I'm understanding the effect a little better. Your rendering of the roots going into the water reminds me of images of penguins swimming under the ice looking up and seeing fish outlined against the blueish light and then darting up to devour them! In those pictures, the space is clearly marked. There's a roof of light and shafts of light penetrating deep below from the ice holes the penguins door to the snow packs.
In that respect, in your image, where there are gaps, columns of light from gaps would help ehhance the effects of your image. Id also try to bring out the edges of the roots. Your picture, I believe, needs more dimensionality to go with your music.
Your music has the sense of some space, a cavern perhaps. However, it has, to my senses, no sounds of water. Not that the two must match, but at least in this version it's something I miss.
As you pointed out, this is just an initial "mess around" not a serious complete idea. However, the concept is a good one. I'd consider this a fair start.
My $0.02
Asher