Let's say you've been messing around in Reason and suddenly found a 2-bar groove you like. Naturally, you won't want to play the exact same two bars throughout your song. Here's how you can create variations. Use CHANGE EVENTS, then get your 2-bar loop and copy and paste until you have an eight-bar pattern. Select the PENCIL TOOL on the MAIN SEQUENCER, then highlight the last four bars and right click on it. Select CHANGE EVENTS and go to alter notes and adjust the value to 25%, 50%, or 75%. Click APPLY and have a listen. Essentially what you're doing is telling Reason to "randomize" the groove. Sometimes you'll get something really cool on the first try, but if you don't like what you hear, click APPLY again to see what Reason comes up with. With patience, you'll eventually land on the perfect variation of your groove!