This came up in discussion today, reminded me of just how incredible this track is. Yes, the Matrix association may give this one an air of cheese to some, but the full 10 minute "Slap It" version released in 2001 is a truly epic slice of ethereal tribal pulsation. There have been a lot of dark, tribal progressive tracks made, but can anyone genuinely name one that sounds quite like?
Even though it really caught my attention when I first heard it in The Matrix it took me years to look up the full version. I could name a few similar-sounding tracks, but I'm not suggesting they are any better or completely capture the same vibe.
These would all be good tracks to mix with Slap It, and I'd include the Jaia track listed above as well, but I don't think any of them have quite the same spacey vastness as Slap It. I think it's one of those tracks with such a unique atmosphere it's hard to select a track to follow that would maintain quite the same vibe - you're forced to "change direction" to some extent.
Another track I'd compare it to, without the tribal prog rumbling, but with the stratospheric acid soundscapes (and sadly never released in full):
The whole Puppy album these tracks feature on is incredible. Was my staple "going out" album for about five years. Amidst the lyrical whimsy and big beat connotations it's easy to forget just how good Fluke actually were.
I discovered this track from Matrix and has been listening to it ever since then, awesome dark stuff.
Mona Lisa Overdrive by Juno Reactor is another awesome track from the same movie.