Another great tutorial by Peak Eleven on using Rex files in Reason:
"Video tutorial on how to use rex files in Propellerheads Reason OctoRex Device. The Rex File format is used for loops that are independent of the tempo. That means that you can load a loop and then choose the tempo in your song. You can also control each slice of the loop, and even play the slices from your keyboard and make your own beat from it. In this video I show a south style hip hop beat and a dirty dubstep beat from rex loops."