Using blends allows you to play between two or more different electronic sounds that are based on the different timbral regions you play on the drum.
To add blends, first click on the pad you want to blend. Then, in the blends panel underneath the pad visualizer click on all of the pads that you want to blend it with. Now those pads will interact with one another - mixing proportionally to how you play the drum.
More on this in the blends section.