It's in the key of Fm (or Ab, I guess), and has some funky changes and fingerings in it. It's a cool sounding tune, though. You can hear the version he recorded with synthesized acoustic guitar here. I'll be recording acoustic guitar to replace the synthesized guitar part (it's the somewhat harpsichorde-ish sounding instrument).
I don't know how long it's been since I've taken on a tune this challenging!