Damn, that kicks ass - very subtle at first, but the unwinding complexity brings a level of depth that belies the simplicity of the base tones. I dig the way you pull a melody out of of the modulation in the beginning. That overlay reminds me of how Xdream uses frog calls.
Since you inquired above, here's something that fits your theme that I wrote a long time ago, Ship of Fools. This was done in FL Studio 9, and you can tell that I just discovered the flanger, and hadn't learned how to properly mix yet, but I'm fond of the tune, and it taught me a lot for my future work.