I cooked up a brief snippet of Archaeopteryx generating ambient drum and bass. It's complete hackery; all I did was set two Arx programs running at the same time. One is my usual drums demo and the other's my ambient music generator from Burning Man last year. Both were sending MIDI to the same Reason setup; all I did to build that was copy a drum machine from my drum demo setup into the setup I used at Burning Man. And of course I had to set both Arx programs to the same tempo. In practice running at the same tempo was impossible, but running at complementary tempos (160bpm and 40bpm respectively) was trivial.
ambient drum & bass demo (4.5mb mp3)