great mood setting background music!
I love how it builds ever so slightly over time instead of being static. the volume of the instruments is well set, the quiet bass strings ( i believe) give a looming, ominous feel to it. I like how it changes slightly too, it isn't just the same loop of sound over and over and over.
Very good for just an experiment!
what about adding a processed choir or metallic screech in? -- with either a sustained note or maybe a slow gradual theme to add a little extra depth.