This was quite fun to do. The original theme is quite simplistic in nature though it layers a lot of instruments and uses reverb to sound "big", resulting in a messy sound. Thus, I may have missed some of the small notes when transcribing it by ear, but I trust I have kept the general spirit of the piece.
So far, there have been two instruments that posed problems - the flute and the harp. The flute, I solved X-files style. I'd say whistling counts as a cappella. I'm sure you all can attest to that I'm a better singer than a whistler. :) whistles innocently off key
The harp, I finally managed to solve by doing a glottal M. and attenuate quickly. The attack I later fixed with Equalization and the decay with excessive reverb. Post-processing is allowed, right? :)
This mix sounds a bit less impressive than the samplers used in the orchestral original, mostly because I need to voice-act and mix better, but also because you can't get mostly-unison choir lines to sound "big" in the same way as with an orchestra (listen to piano renditions of Hans Zimmer's work. It's not very impressive.) For a final version, I'd likely arrange it more choir-style instead of faithfully following the original.