1st track sets the vibe quite well with some interesting synths -- 2nd track adds some strangeness to the mix, 3rd has a very cool underground vibe as you've described -- overall the sounds you use for this are quite relaxing, 4th track adds a bit of intensity (but not very much) 5 returns us essentially to the beginning.
Overall I don't really hear the correlation to theme but it was nice, very creative use of sounds though