EDIT: Ok, I NOW hear what you mean. There is a very subtle kind of ambience there. Could be a faint chorus that modulates. It is though quite subtle.
EDIT2: The first clap has a tiny "squeak" thing going on. Like a heavy pitch modulation of the surrounding ambience. Hmm.. interesting question, what could do this? It does seem to be a bit random.. kind of. Try a combination of haas effect, (a simple opposite side delayed signal of less than 30ms) with a modulation delay and together with some slight flanger or chorus (keep the wet level very low).
- bManic

